JANIS 75 JOINT ARMY-NAVY INTELLIGENCE STUDY OF KOREA

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP79-01144A000900010001-1
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 82
• Document Creation Date: December 19, 2016
• Document Release Date: May 26, 2006
• Sequence Number: 1
• Publication Date: April 1, 1945
• Content Type: STUDY

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JANIS 15
Volume No. 1 of 2
4
?
Non-registered
JOINT ARMY
INTELLIGENCE
.017
,
- NAVY
STUDY
A
K ?
(Including Tsushima and Quelpart)
JOINT INTELLIGENCE srmy PUBLISHING BOARD
April ? 1945
-
r
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?
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JOINT INTELLIGENCE STUDY PUBLISHING BOARD
Washington, D. C.
MEMORANDUM
15 April 1945
Subject: JANIS 75
1. Joint Army-Navy Intelligence Study of KOREA (Including Tsushima and
Quelpart) is promulgated herewith.
2. This is a confidential non-registered publication. Three chapters have been
classified restricted in order to facilitate their distribution among interested person-
nel. The publication contains information affecting the national defense of the United
States within the meaning of the Espionage Act, 50, U.S.C. 31 and 32, as amended. The
transmission or the revelation of its contents to an unauthorized person is prohibited
by law.
3. When complete, JANIS 75 will comprise Chapters I to XV, inclusive, (Vol. 1 of
2) and a Plans Pouch (Vol. 2 of 2) containing reference maps.
4. As a means of expediting distribution, the various chapters will be issued as
they come off press, not necessarily in numerical order.
5. It is anticipated that the issue will be complete by I May 1945. As
the several chapters are received, they should be arranged in numerical order in the
binder provided, and date of receipt entered in the spaces below. Titles of the
chapters will be:
Chapter I - Brief
Chapter II - Military Geography (Restricted)
Chapter III - Oceanography
Chapter IV - Coasts and Landing Beaches
Chapter V - Climate and Weather
Chapter VI - Port Facilities
Chapter VII - Transportation and Telecommunications
Chapter VIII - Cities and Towns
Chapter IX - Resources and Trade
Chapter X - People and Government
Chapter XI - Health and Sanitation (Restricted)
Chapter XII - Defenses
Chapter XIII - Naval Facilities
Chapter XIV - Air Facilities
Chapter XV - Gazetteer and Map Appraisal (Restricted)
6. Table of Contents and List of Effective Pages of each chapter are given in-
side the chapter covers. A combined List of Effective Pages will be included with the
final distribution. A list of the plans is issued with the Plans Pouch.
7. (a) The distribution of this publication to naval activities is effected
through the Registered Publications Issuing Offices, and requests for copies not
included in registered publication allowance tables should be addressed to the Division
of Naval Intelligence.
(b) The War Department will distribute this publication to army units,
and requests from army units should be directed through army channels.
Joint Intelligence Study Publishing Board
Chapter
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
.
XIII
XIVXV
Plans
Date Rec'd
,
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;
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JANIS 15
CHAPTER 1
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BONIN IS.
JOINT ARMY-NAVY INTELLIGENCE STUDY
OF
KOREA
(INCLUDING TSUSHIMA AND QUELPART)
BRIEF
APRIL 1945
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List of Effective Pages, Chapter 1
CHANGE IN
SUBJECT MATTER EFFECT
Cover Page Original
List of Effective Pages and Table of Contents, Chapter I
(inside front cover) Original
Text and Figures Original
Text (reverse blank) Original
Figures (inserts, reverse sides blank) Original
Imprint and Table of Contents (Coned) (inside back cover,
reverse blank) Original
PAGE NUMBERS
unnumbered
unnumbered '7
PP . I-1 to 1-46
p. 1-47
Figures 1-15 to 1-44
unnumbered
Table of .Contents
Note: This chapter is based on material available in Washington, D. C., on 1 March 1945.
FORE WARD
1. INTRODUCTION
A. Position
B. Terrain
C. Climate
D. Economic regions
E. Principal routes
F. Important nuclei
(1) Central and northwestern centers
(2) Southern centers
(3) Northeastern centers
G. People and government
2. MILITARY GEOGRAPHY
A. Relief
(1) General character
(2) Regional divisions
(3) Mountains and hills
(4) Lowlands
B. Drainage and water supply
(1) Rivers
(2) Lakes and marshes
(3) Water supply
C. Soil trafficability
(1) Terrain and soil trafficability
(2) Weather and soil trafficability
D. Vegetation
(1) Mixed deciduous broadleaf and coniferous forest
(2) 13roadleaf forest
(3) Cultivated areas
(4) Barren sections
(5) Marshlands
(6) Effect of vegetation on operations
E. Significant areas
F. Routes to significant areas
3. OCEANOGRAPHY
A. Regional considerations
B. Seasonal considerations
4. COASTS AND LANDING BEACHES
A. East coast
B. South coast
C. West coast, southern and central parts
D. West coast, northern part
5. CLIMATE AND WEATHER
A. Storms
B. Precipitation
C. Temperature
D. Humidity
Page
I - 3
I - 5
I - 5
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1 - 16
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Page
E. Surface winds I - 18
F. Winds aloft I - 19
G. Cloudiness I - 19
H Ceilings I - 20
I. Turbulence I - 20
J. Icing I - 21
K. Visibility I -
6. PORTS I - 2.1
A. Introduction and summary I - 21
B. Principal ports I - 23
(1) Unggi (Yaki) I - 23
(2) Najin (Rashin) I - 23
(3) Ch'ongjin (Seishin) I - 23
(4) Songjin (jOshin) I - 24
(5) Hungnam (Konan) I - 24
(6) Wonsan (Cienzan) I - 24
(7) Pusan (Fuson) I - 24
(8) Kunsan (Gunzan) I - 25
(9) Inch'on (Jinsen) I - 25
(10) Chinnamp'o I - 25
C. Secondary ports I - 26
(1) Sosura (Seisuira) I - 26
(2) Odaej in-hang I - 26
(3) Yongom-ni (Yonam-ni) I - 26
(4) Ch'aho (Shako) I - 26
(5) Sinch'ang (Shinsho) I - 26
(6) Sinp'o (Sh.nho) I - 26
(7) Kojo-p'o (Kotei-ho) I - 26
(8) Changjon-hang (Chosen-ko) I - 26
(9) Taep'o-ri (Taiho-ri) and Sokcif o-ri
(Tongch-'0-ri) I - 27
(10) Chumunjir I - 27
(11) Mukhojin-ni (Bokukoshin-ri) I - 27
(12) P'ohang-dong (Hoko-do) I - 27
(13) Kuryongp'o-ri (Kylariiho-ri) I - 27
(14) Kamp'o-ri (Kanho-ri) I - 27
(15) Pango-ri (Hogyo-ri) I - 27
(16) Ulsa.n-man (Urusan-wan) I - 27
(17) Chisep'o, Changsung-p'o, and Nung-. I - 27
(18) Masan I - 28
(19) T'ongyong (Thei) I - 28
(20) Samch'orn-l'o (Sanzenho) I - 28
(21) Yosu (Reisui) I - 28
(22) Mokp'o (Moppo) I 28
(23) Yongdangp'o (Rya-toho) I - 28
(24) Kyomip'o (Kenjiho) I - 29
(25) Dasado (Taedasa-do, Tashin5) ... . I - 29
(26) Yongamp' o (Ryagarnpo) . ... . I - 29
(27) Sinuiju (Shingishu) An-rung I 19
(Continued on Inside Back Cover)
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BRIEF
Pagel- 1
70?
80?
90?
100?
1100 120? 130? 140? 150? 160? 170? 180?
170?
AREAS COVERED BY PUBLISHED
JOINT ARMY-NAVY
INTELLIGENCE STUDIES
(With the exception of Janis 38, BULGARIA)
0 500 1000 MILES
APPROXIMATE SCALE
Sinusoidal Equal Area Projection
10?-
1
90? 100? 110?
120? 130? 140? 150? 1
FIGURE I - I.
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BRIEF:
LOCATION MAP OF KOREA
Radial Scale From Kyongsbrif (Keii5) or (Seoul)
0 500
1000
1500 2000
STATUTE MILES
STEREOGRAPHIC PROJECTION CENTERED ON KYONGSoNG (KEIJo) OR (SEOUL)
?
1/0" 125? 30? 140? 1500
50 F4 100? 110
00? 480? exifi
04
A *44biI
40?
5?
160?
170?
180?
50?
4
45,
40?
M A N
35?
30?
25?
KOREA JAPA
s'OrkK (14S96
or (Secti',
YELLOW
tbkv7)
10?
SEA
40.
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15?
railNAEAST
S44
9FORMOSA
PHIUFFINE
Manila
10?
Po.
;ISLANDS
0?
95?
1
105?
110?
NE
115?
120?
Palau Is.
?
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11.
?
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ocP'b\
WANE
S
25?
20?
15?
10?
125? 130?
135?
140?
145?
150?
FIGURE
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4011.1m mow Chapter I
Page 1-3
BRIEF
Foreword
The purpose of this study is to make available, subject to limitations of time and material, one publication containing all the
necessary detailed topographic information upon which may be based a plan for military operations in Korea. The study is in-
tended also to provide an organized presentation of material to be used as a base on which to plot later information obtained
from aerial reconnaissance and other sources available in the field. Data available in Washington up to 1 March 1945 have been
incorporated in the study. A list of principal sources will be found at the end of each chapter except Chapter I. Correct diacritical
markings of place names are found in the Gazetteer, Chapter XV. Because of typographical difficulties, the breve was omitted
over the Korean o and u in all other chapters.
To meet the varied requirements of users, the material is presented in two distinct patterns. Chapter I, entitled "Brief," is a
condensation of the material presented in much greater detail in the succeeding chapters. It provides a "quick look," complement-
ing the main body of the study.
This publication has been prepared from material contributed by a number of agencies of the United States Government, in-
cluding the following: Aerology Section, Office of the Chief of Naval Operations; Assistant Chief of Air Staff, Intelligence; Board
on Geographical Names; Coast and Geodetic Survey; Hydrographic Office; Joint Meteorological Committee; Military Intelligence
Division; Office, Chief of Engineers (Army Map Service, Beach Erosion Board, Board of Engineers for Rivers and Harbors, Ge-
ological Survey); Office of Naval Intelligence; Office of Strategic Services; Office of the Surgeon General; Weather Division,
Army Air Forces.
For convenience, contents have been made up in two volumes: Volume 1, text, and Volume 2, Plans Pouch. A table of con-
tents will be found on the inside cover of each chapter. The text includes the following 15 chapters, all of which are "Confi-
dential" except II, XI, and XV, which are "Restricted."
CHAPTER I BRIEF
CHAPTER II MILITARY GEOGRAPHY
CHAPTER III OCEANOGRAPHY
CHAPTER IV COASTS AND LANDING BEACHES
CHAPTER V CLIMATE AND WEATHER
CHAPTER VI PORT FACILITIES
CHAPTER VII TRANSPORTATION AND TELECOMMUNICATIONS
?CHAPTER VIII CITIES AND TOWNS
CHAPTER IX RESOURCES AND TRADE
CHAPTER X PEOPLE AND GOVERNMENT
CHAPTER XI HEALTH AND SANITATION
CHAPTER XII DEFENSES
CHAPTER XIII NAVAL FACILITIES
CHAPTER XIV AIR FACILITIES
CHAPTER XV GAZETTEER AND MAP APPRAISAL
FIGURE I - 1 shows the areas covered by this and previously published JANis studies.
JOINT INTELLIGENCE STUDY PUBLISHING BOARD
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Page I - 4
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BRIEF
FIGURE I - 3, Korea.
Vertical view Of model.
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Page 1 - 5
FIGURE I - 4. Korea.
Oblique view of model, looking northward.
I. Introduction
A. Position.
Korea (ChEisen) is a long peninsula extending southeast-
ward from Manchuria (FIGURES I - 3 to I - 5). It lies in the
midst of Japanese-held territory: Manchuria along the north-
west border, China across the Yellow Sea to the west, and the
main islands of Japan across the Sea of Japan and Korea Strait
to the eastward (FIGURE I - 2). The only break in the Japanese
encirclement is in the northeastern corner, where Korea ad-
joins the U. S. S. R. for a distance of about 10 miles. Vladivostok
is about 80 miles distant from this corner of Korea.
Korea provides Japan with important amounts of food and
raw materials, a strategic military supply base, and a link of
railroads between Japan proper and her military forces on
the Asiatic mainland.
B. Terrain.
The northern third of Korea is occupied by a mass of rough
mountains separated from Manchuria by the deeply trenched
valleys of the Amnok-kang and Tuman-gang (FIGURE I - 5).
Southward from these mountains the Taebaek Range, a long
barrier of lower mountains, extends to the end of the peninsula
keeping close to the east coast.
Mountain and hill spurs branch from the Taebaek Range
westward to the coast of the Yellow Sea. The principal low-
lands of Korea lie between these mountain spurs. The low-
land of the Naktong-kang (river) opens upon the south
coast, but all other large lowlands border the west coast. All
the long rivers of Korea, except the Tuman-gang in the north,
flow westward from the Taebaek Range and wind through the
lowlands. The roughness of the mountains and the wetness of
the lowlands with their large rivers and irrigated fields are
serious hindrances to movement.
FIGURE I - 5. Korea.
Oblique view of model, looking southward.
The south and west coasts are highly irregular, with alter-
nate beach-fringed lowlands and rocky headlands, and numer-
ous offlying islands, rocks, reefs, and shoals. Broad drying mud
flats and sand bars, and a large tidal range, add to the difficulty
of approach along the west and south coasts. The largest islands
are Tsushima (politically part of Kyilishil) and Cheju-do
(Saishii-tO, Quelpart), in the Korea Strait.
In contrast to the west and south coasts, the east coast is
fairly regular, with small beach-bordered pocket valleys sepa-
rated from one another and from the interior by steep moun-
tains with swift streams; approaches from the sea are rela-
tively clear.
C. Climate.
Korea is hot and wet in summer, cold (below freezing) and
fairly dry in winter. The climate of Kyongsong (Keijo, Seoul)
about midway of the area, north and south, closely resembles
that of Des Moines, Iowa, except that in summer Kyongsong
receives about 3 times as much rainfall as Des Moines. Cross-
country trafficability is best in fall and winter. Rivers in the
northern half of Korea freeze in winter, but ice does not form
in the harbors except in the northeast, where movement of
small boats is sometimes hampered by ice; and in the north-
west, where river ports, including Sinuiju (ShingishU) and
Chinnamp'o, are closed by ice part of the winter. The season-
ally reversing wind?northerly in winter, southerly in summer
?affects shipping on windward coasts.
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BRIEP Confidential
D. Economic regions.
The Korean population is concentrated chiefly in the low-
lands of the west and south, which are utilized for intensive
agriculture, especially paddy rice production. About 3/4 of the
people of Korea depend upon agriculture, and a considerable
amount of rice, other food, and cotton is exported to Japan.
Some cities of central Korea, especially the Kyongsong (Keija,
Seoul) ? Inch'on ( Jinsen) ? Pup'yong (Fuhei) district have
important metal-working industries.
Northern ,Korea, though less densely populated than the
rest of the country, is the principal industrial region because
of its large resources of hydroelectric power, iron and other
ores, coal, and timber. The principal iron mines are at Musan
(Mozan) in the far northeast. Coal and iron ore are exported
in considerable quantities to Japan proper. Production of chem-
icals (the leading manufacture of Korea in terms of value),
iron, and steel are important industries in the northeast.
E. Principal routes.
The most important artery of transportation in Korea is the
double-track railroad running from Pusan in the southeast
corner of the peninsula to the Manchurian border at Sinuiju ?
An-tung in the northwest corner, and thence to Mukden. This
railroad links the chief lowlands and the three largest cities of
Korea and provides rapid communication between Japan proper
and Manchuria. The railroad has many vulnerable bridges. Sev-
eral brancheS connect the main line of the railroad with ports
on the west coast.
Another railroad skirts much of the coast of northeastern
Korea, and Connects with cross lines running into Manchuria.
These cross lines have become very important for military
traffic to Manchuria and for the development of resources and
industries in northern Korea.
The rail'systems of the west and the east coasts are con-
nected with one another by two cross lines winding through
the mountains. The most important of these lines runs south-
ward from Wonsan (Genzan) to Kyongsong (Keija, Seoul)
traversing the mountains by way of a natural corridor; the other
runs westwapd from Wonsan to P'yongyang (Heija).
Korea does not have an extensive net of all-weather roads.
The use of automobiles has never been widespread, and the
roads have been laid out chiefly from the military viewpoint.
The main road arteries form a great X intersecting at Kyong-
song and extending to the four corners of the peninsula, one
highway running from Pusan to Sinuiju, and the other from
Mokp'o to Onsong (Onja) by way of Wonsan. Some of the
few hard-surfaced roads connect major cities with their nearby
ports. Most of the motorable roads are made of macadam.
Spring thawS, summer rains and floods, and, in the mountains,
landslides, often impede traffic on ordinary roads.
Much Korean transport is handled by coastal shipping. Active
trade with japan proper is carried on through all major ports.
F. Important nuclei.
Eleven of the 15 Korean cities with population of more
than 50,000, are situated on or adjoining the western and
southern lowlands. The other, 4 are on the northeast coast.
Ch'ongjin, Najin, Wonsan, Pusan, Kyongsong, and Sinuiju ?
An-tung are! particularly vital strategic centers.
(1) Central and northwestern centers.
, By far the largest and most important city is Kyongsong
(Keija, Seoul), the capital of Korea and the only city with a
population approaching one million. It is about 20 miles in-
land from the west coast about midway between the northern
and southern ends of the coast, at the inner edge of a lowland.
It is the principal railway and road hub of Korea and, together
with its rapidly growing suburbs, manufactures railroad equip-
ment and other heavy machinery. The port for Kyongsong is
Inch'on (Chemulpo, Jinsen), fourth largest city of Korea, with
important steel and machinery manufacturing.
P'yongyang (Heijo), second largest city of Korea, is another
lowland city, about 120 miles northwest of Kyongsong. It is
ain industrial and railroad center, and has Korea's chief arsenal
and army airbase. Its port, Chinnamp'o, has chemical and non-
ferrous metallurgical industries, based upon the mineral and
power resources of the northwestern region, and is the principal
naval coal depot of Korea.
On the northwest border is the strategic city of Sinuiju
(Shingisha) which, together with the larger city of An-tung
across the border in Manchuria, forms a single urban complex.
Two major bridges on the main railroad cross the Amnok-
kang (Yalu River) here. Sinuiju is a center of lumbering,
Mining, and new industrial development. An ice-free port has
recently been developed for this area at Dasado (Taedasa-do,
Tashita), on the coast just south of the mouth of the Amnok-
hang (Yalu River).
(2) Southern centers.
In southern Korea the most important center is Pusan (Fu-
san) , third largest city and most vital port of the country. It
is the key transshipment point on the fastest water and land
route from Japan proper to Manchuria. At Pusan the main
Korean railroad meets the vital freight and passenger ferry
rom Shimonseki, Honshu. Pusan is also the center through
which the principal concentration of cables connects Korea
,ivith Japan proper. The distance from Pusan to Shimonoseki
across the Korea Strait is 120 miles. Pusan is the chief ship-
building center of Korea, and has important munitions, iron
4nd steel, and oil refining industries.
Sixty miles inland from Pusan is Taegu (Taikya), the larg-
est inland city of southern Korea. Taegu lies in the heart of
the chief southward-facing lowland, and is an important po-
litical, textile, commercial, and transportation center.
Twenty miles west of Pusan is Chinhae (Chinkai), which
has the principal naval base of Korea, the headquarters for the
guard district covering the entire south and west coasts, and a
Major air depot. Chinhae has unlimited protected anchorage.
Still farther west is Yosu (Reisui), recently developed as a
military and naval center and connected with the main rail
system of western Korea.
The two large islands off the south coast of Korea have
Important military installations. Aso-wan (Tsushima Sound),
in Tsushima, is fortified, and the minor naval base on Aso-wan
may have been reestablished. Cheju-do (Saisha-ta, Quelpart)
is important as an airbase between Japan and China.
In the southwestern part of the mainland the two chief ports
are Mokp'o (Moppo) and Kunsan (Gunzan), both of which
export rice from the Korean lowlands to Japan proper. Kwang-
ju (Kasha), a transportation center, is the principal inland
city of the southwest.
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(3) Northeastern centers.
The rapid development of the power and mirieral resources
of the area, and the increasing military importance of Man-
churia and the Russian border region, have led to rapid recent
development of cities in northeastern Korea. Six of the 10 prin-
cipal ports of Korea are concentrated on this coast.
The 3 northernmost principal ports?Unggi (Yiaki), Najin
(Rashin), and Ch'ongj in ( Seishin) ?have special military im-
portance because of their direct rail connections with the Man-
churian railroad center of T'u-men, just across the border from
Korea. In addition, Unggi and Najin lie only about 10 and 20
miles, respectively, from the Russian border. Najin (Rashin),
a very large port, has a naval base and major naval coal and oil
depots, and is the headquarters for naval administration on the
east coast. Ch'ongjin (Seishin), with a population of about
200,000, is the largest city of the east coast. Ch'ongjin has ex-
tensive traffic between Japan and Manchuria, is the outlet for
iron ore from the great Musan mines, and has important new
iron and steel industries.
Two other principal ports, Hungnam (Konan) and Wonsan
(Genzan), lie on the northern and southern sides, respectively,
of Tongjoson-man (Higashi-Chosen-wan, Choson-haeman), the
large gulf opposite the narrowest part of the Korean Peninsula.
Hungnam (Konan) is the center of Korean manufacture of
chemicals, including munitions. It is the largest producer of
nitric acid, glycerine, sulphuric acid, and magnesium in the
Japanese Empire. Wonsan (Genzan) is the east coast terminus
of the rail and highway routes that lead through the mountains
to Kyongsong and P'yongyang on the western lowlands. Won-
san has a harbor with unlimited anchorage, a naval base, a
fuel oil and coal storage base, and the principal petroleum re-
fineries of Korea.
G. People and government.
The Koreans are much like the Chinese in culture, but they
have their own language. Since the annexation of Korea by
Japan in 1910, the Japanese have controlled the government
and the police. Japanese now constitute about 3% of the total
population of Korea and 10% to 20% of the population of
the cities. Though the Japanese police have eliminated open
activity of independent Korean organizations such as labor un-
ions and political parties, a strong spirit of resistance and a de-
sire for independence continue to exist among the people.
Guerrillas are active in the northern highlands, and under-
ground resistance is organized in the cities.
2. Military Geography
The basic maps for use with this topic are FIGURES I - 15
to I - 20. In addition, PLANS 4, 5 to 34, and 48 to 51, in PLANS
POUCH, together with ROUTE SUPPLEMENT FIGURES RS-5,
RS-6, RS-11, RS-13, RS-16, RS-19, RS-20, and RS-21, in
ROUTE SUPPLEMENT POUCH, comprise a medium-scale (most-
ly 1:250,000) topographic map of the entire area.
A. Relief.
(1) General character.
Korea is a mountainous, S-shaped peninsula extending south-
ward from Manchuria and Siberia toward Kydsha (FIGURES
I - 3 to I - 5, and I - 15 to I - 18). From its northeastern
border along the Tuman-gang due south to Pusan, Korea ex-
tends about 525 miles. Its width east ? west varies from 125
to 200 miles, and its area is estimated at 85,000 square miles.
The Korea Strait, which separates the peninsula from the main
islands of Japan, is about 125 miles wide. Most of the northern
boundary of Korea is formed by the deeply entrenched and
winding Amnok (Yalu) and Tuman Rivers. Manchuria touch-
es all this boundary except the easternmost 10 miles of the
Tuman-gang where the Maritime Province of Siberia adjoins
Korea.
Several large islands and hundreds of small islands lie off
the peninsula. About 80 miles off the east coast is Ullung-do,
a rugged, shield-shaped island. The 2 islands of Tsushima are
about half way between Korea and Kyashta. Cheju (Quelpart
Island) lies 50 miles off the southwest corner of the peninsula.
Hundreds of steep, rugged, small islands lie off the south and
west coasts.
The east coast of Korea faces the Sea of Japan and is mostly
steep and rugged, with small pocket lowlands separated by
hills or mountainous promontories. The south coast faces the
Korea Strait. This coast is deeply indented and very irregular.
The west coast faces the Yellow Sea. It is mostly low, is greatly
indented, and has a 1- to 5-mile-wide belt of mud flats exposed
at low tide.
The relief pattern of Korea is dominated by the following
highland elements: ( ) A large mountain mass in the north
and northeast, (2) a long nearly continuous mountain bar-
rier extending southward from these northern highlands, arid
bordering the full length of the east coast, (3) several tribu-
tary ranges and spurs extending southwestward from the main
east coast range.
Only a small part of Korea is lowland (FIGURE I - 17).
The lowlands are similar to each other in many respects, but
vary in size and have special characteristics depending upon
position. They are found in 5 general locations on the penin-
sula: (1) Along the lower Tuman-gang and Amnok-kang
Valleys in the north, (2) forming a series of small, discon-
nected pocket lowlands along the east coast, (3) in the
Naktong-gang Basin, inland from Pusan, (4) in a discon-
tinuous belt along the south coast, (5) forming a series of 5
large and important lowlands along the western side of the
peninsula. Each of the western lowlands is separated from its
neighbor by a zone of mountains, hills, or ridges.
The mountain framework, because of its location and align-
ment, tends to restrict movement in any direction. The North-
ern Korean Highlands and the long, north ? south-trending
Taebaek Ranges make east ? west, cross-peninsular, large-
scale movement virtually impossible. The only significant east ?
west passageway extends between Wonsan and Seoul (Kyong-
song, Keijo), but even this is locally narrow and steep (FIGURE
I - 16). The tributary spurs, of which the Sobaek Range ex-
tending southwestward from the Taebaek Ranges is the most
important, present a series of potential natural defensive posi-
tions at intervals of 10 to 30 miles across lines of north ? south
movement on the western side of Korea. Similarly, the steep
ridges or hills separating successive small pocket lowlands at
intervals of 1 to 6 miles along the east coast constitute a series
of natural defensive positions across a line of north ? south
movement there. The winding rivers of western Korea, when
at flood, also form obstacles to north ? south movement. Such
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rivers as the Kum, the Han, the Imjin, the Yesong, the Tae-
dong, and the Ch'ongch'on have channels 200 to 2,000 yards
wide (FIGURE I - 15).
(2) Regional divisions.
The terrain regions referred to in subsequent paragraphs
are shown in FIGURES I - 15 to I - 17, and I - 19. The regions
and subregiOns are:
1. Region 1. Lower Tuman-gang Valley.
2. Region 2. Eastern Coast Lowlands and Hills.
3. Region 3. Northern Korean Highlands.
Subregion 3a. Eastern Hills and Mountains.
Subregion 3b. Kaima Plateau.
Subregion 3c. Yangnim Range.
Subregion 3d. P'yongan-pukto Hills and Mountains.
4. Region 4. Northern Taebaek Range.
5. Region 5. Wonsan-Seoul Corridor.
6. Region 6. Southern Taebaek Range and Sobaek Range.
7. Region 7. Naktong-gang Basin and Hills.
8. Regibn 8. Southern Coast Lowlands, Hills, and Islands.
9. Regibn 9. Island Approaches.
Subregion 9a. Ullung-do.
Subrpgion 9b. Tsushima.
Subfegion 9c. Cheju-do.
10. Region 10. Western Lowlands and Hills.
Subregion 10a. Cholla-namdo and Cholla-pukto Hills.
Subregion 10b. Kum-gang Basin and Valley.
Subregion 10c. Ch'ungch'ong-namdo and Ch'ungch'ong-pukto
Hills.
Subregion 10d. Han-gang Basin and Valleys.
Subregion 10e. Kyonggi-do Hills.
Subregion 10f. Imjin-gang and Yesong-gang Valleys.
Subregion 10g. Hwanghae-do Hills.
Subregion 1011. Taedong-gang Valley.
Subregion 10i. P'yongan-namdo Hills.
Subregion 10j. Ch'ongch'on-gang Valley.
Subregion 10k. P'yongan-pukto Hills.
11. Region 11. Lower Amnok-kang Valley.
A regional summary table of relief, drainage, vegetation,
soil trafficability, and climate is included in PLAN 3.
(3) Mountains and hills (FIGURE I - 17 ) .
The 3 major highland regions of Korea are (a) the north-
ern mountain ranges; (b) the ranges of the peninsula includ-
ing the Northern Taebaek Range, the Southern Taebaek
Range, and its appendage, the Sobaek Range; and (c) the
lower, hilly spurs, which extend southwestward from the main
mountain systems. These hilly spurs separate the various basins
and valleys of the southern and western coast.
(a) Northern mountain ranges. These mountains com-
pose the Northern Korean Highlands (Region 3) and are a
continuation of the mountains of southern Manchuria. Their
drainage is mostly northward toward the Amnok and the
Tuman, whose deeply entrenched and sinuous valleys form
the greater part of the boundary with Manchuria. The high-
lands are largely rugged, steep, and rocky, but include areas
of gently sloping upland, at elevations of 4,500 to 6,500 feet.
These uplands, comprising the Kaima Plateau, are a conspicu-
ous feature of the area southeast of Paektu-san. Although the
undulating upper surfaces of the Kaima Plateau are favorable
for movement, they are set apart by steep valley sides and are
practically isolated. Except for these flattish uplands the
Kaima Plateau is very unfavorable for movement. The east-
ernmost and westernmost parts of the Northern Korean High-
lands have rolling to steep hills and mountains, generally 1,000
to 3,000 feet high, with winding, U-shaped iralleys as much
as a mile wide. Passes on principal routes are 1,600 to 2,300
feet high. These eastern and western extremities are generally
more favorable for movement than the very broken Kaima
Plateau and the very rugged Yangnim Range which lie be-
tween them. The Yangnim Range is the highest and most in-
accessible portion of the Northern Korean Highlands Region.
Summit elevations range from 5,000 to more than 8,000 feet;
almost all slopes are steep; valleys are narrow and very wind-
ing. Passes on principal routes are 3,500 feet or more in eleva-
tion.
In general, the terrain in the Northern Korean Highlands
is unfavorable for movement. The winding valleys offer only
limited possibilities for movement and the hills and mountains
are very difficult. Natural routes are largely concentrated in
the eastern and western parts of the region.
(b) Peninsular highlands. The peninsular ranges include
the Northern Taebaek and the Southern Taebaek with its
largest appendage, the Sobaek Range. The Northern Taebaek
ange is a southward extension of the Northern Korean High-
lands. Here the ridges trend mostly north - south, but the val-
leys extend in all directions. The region is rugged, partly
forested and well drained, but unfavorable for cross-country
movement. The hills and ridges are generally 1,500 to 5,000
feet high, and are steep. Valleys are narrow, gorge-like, and
extremely winding. In their upper reaches the larger westward-
flowing rivers, such as the Ch'ongch'on, the Taedong, the
yesong, and the Imjin, flow in narrow, steep-sided valleys or
gorges which provide no room for extensive movement or de-
ployment. The hill and mountain slopes are very unfavorable
to cross-country movement. No routes suitable for rapid, large-
scale movement cross this region in any direction. Existing
toads are narrow and winding, and cross steep passes 2,000
to 3,600 feet high. Separating the North and South Taebaek
Ranges is the Wonsan-Seoul Corridor, the most favorable pas-
age between the east and west coasts.
South of the corridor is the Southern Taebaek Range. This
is a continuation of the Northern Taebaek Range and is sim-
ilar in character-steep and rugged, with narrow, winding,
gorge-like valleys. Summit elevations are generally 2,000 to
,000 feet. Most of the ridges and valleys are aligned north -
south, although the region as a whole trends northwest -
southeast.
The Sobaek Range is a southwestward extension of the
Southern Taebaek Range. It lies across the routes from Pusan
to Seoul. Terrain at higher elevations in the Sobaek is rugged,
like that of the Taebaek, but the average elevation is lower
(2,500 feet) and a greater area has moderate slopes. The
river valleys are wider, particularly in their lower reaches, but
there is little flat land in the Taebaek or in the Sobaek; nearly
all the surface is sloping. The small areas of flat land in the
Valleys are irregular in si-e and shape and are discontinuous.
In general, the highland terrain of the peninsula is unsuit-
able for cross-country movement. Steep, eroded slopes, and non-
trafficable soils resulting from heavy summer rains, are unfav-
orable factors for movement in the lower hills. In the higher
areas, cliffs, very steep slopes, and rugged terrain resulting
from extensive erosion make cross-country operations almost
'mpossible. Even on the flat valley floors, movement is ham-
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pered by the winding character of the streams, by floods, and
by wet rice fields.
All east ? west routes across the Southern Taebaek are steep,
narrow, winding, and cross passes at least 1,200 feet high.
These routes probably are unsuitable for heavy, two-way traffic.
Three of the main north ? south routes of Korea cross the
Sobaek Range. All three are locally narrow and winding, and
cross passes 330 to 1,600 feet high.
(c) Hill country. The southwestward-trending hilly spurs
extending from the main mountains toward the south and west
coasts separate the various southern and western lowlands, and
are discussed below.
(4) Lowlands (FIGURE I - 17 ) .
Korea's lowlands are relatively small and most of them are
nearly surrounded by hills and mountains. The largest and
most productive of them are found in the west and south, and
are associated with the larger rivers, such as the Taedong, the
Han, the Kum, and the Naktong. Each lowland is flat or gently
sloping, intensively cultivated, and drained by a main stream
and smaller tributaries. Many lowlands are protected from
flood waters by dikes. The largest lowlands are 25 to 30 miles
wide and may extend 30 to 50 miles inland; the smallest are
about a mile wide and extend 3 to 5 miles inland.
(a) Northern border lowlands. Both the Lower Tuman
Valley (Region 1) on the northeastern border, and the Lower
Amnok-kang Valley (Region 11) on the northwestern border
are winding, entrenched, steep-sided, and flanked by hills and
mountains. Neither lowland provides continuously favorable
terrain for movement inland. Existing routes are successively
close to the rivers and several miles away, among the hills.
These regions have military importance because of their situa-
tion along the Siberian and Manchurian borders.
(b) Eastern coastal lowlands. The Eastern Coast Low-
lands and Hills (Region 2) includes a series of semi-isolated
pockets near the mouths of streams. These lowlands are gener-
ally flat, intensively cultivated, 1 to 6 miles broad, and ex-
tend 3 to 8 miles inland. Along the shore they generally
have a cobbly beach, backed by dunes or a lagoon. On the
land side they are surrounded by steep, partly forested hills
or mountains. Each lowland pocket narrows inland into a wind-
ing, steep-sided valley. The largest and most important of
these is between Hamhung and Wonsan and leads inland to
the Wonsan-Seoul Corridor.
(c) Southern interior lowlands. The Naktong-gang Basin
(Region 7) in the southeastern part of Korea, contains an
extensive area of lowland. This lowland borders both sides of
the Naktong-gang and of its major tributaries, and varies in
width from a few yards to 8 to 10 miles. It provides a low but
very winding route 125 miles into the peninsula from the
Naktong delta near Pusan. Dikes and levees up to 15 to 20
feet high protect the cultivated parts of the valley from flood
waters. The uncultivated parts are covered with sand, cobbles,
or boulders and are nearly bare of vegetation. The cultivated
parts produce a variety of crops, chiefly rice. Rolling, much
eroded hills overlook all of this lowland. Above the hills,
steep mountains, 3,000 to 4,000 feet high, rise as conspicuous
landmarks. Lowland terrain conditions favor cross-country
movement except on the wet rice fields and during wet sum-
mer weather. Existing routes are not steep, but are very wind-
ing. The principal Pusan-Seoul road and rail routes cross the
region.
(d) Southern coastal lowlands. The Southern Coast Low-
lands, Hills, and Islands (Region 8) includes several small
lowlands, most of which are situated at the heads of bays.
These lowlands trend mostly north ? south, occupying the val-
leys of the Somj in-gang and smaller streams to the east and
west. They are 1 to 5 miles wide and 3 to 8 miles long. Numer-
ous small, flat lowland areas are planted almost entirely to
rice, but some low areas are barren river flood plains, or are
planted to dry crops.
Low, steep, gullied hills separate the numerous small low-
land areas. On the south, winding, rugged peninsulas enclose
the bays, and hundreds of rugged islands dot the bays and
guard the coast to a distance of 50 miles offshore. On the
north, west, and east, steep, gullied hills and mountains sur-
round the lowlands and confine the routes between them.
Some of the larger bays at whose heads the lowlands begin
are Chinhae-man, Kwangyang-man, and Tungnyang-man.
Among the largest islands offshore are Koje-do, off Chinhae-
man (Masan); Namhae-do, near Kwangyang-man (Yosu) ;
and Chin-do, near Mokp'o. The most favorable areas for cross-
country movement are those lowlands which are not in rice,
and the lower hills. The rice paddies are unfavorable for
movement when wet, and most of the hills are gullied and
steep. Existing road and rail routes lead mostly northward
toward Seoul. The roadways are not steep but are very wind-
ing. The east ? west, coastal road follows a devious route,
skirting the shore, turning inland to avoid hills, crossing some
lowlands but avoiding rice fields, and crossing passes less
than 1,000 feet high.
(e) Western lowlands. The 5 major lowlands in the
Western Lowlands and Hills (Region 10) are the most exten-
sive in Korea. They trend mostly northeast ? southwest. The
largest are 25 to 30 miles wide and extend 30 to 50 miles
inland. Rolling and steep hills and ridges separate the various
lowlands from each other and constitute potential natural de-
fensive positions blocking north ? south movement. The lower,
broader coastal basin sections of the lowlands are mostly
bordered by hills even on the sea side, and generally have re-
stricted outlets to the coast. The slightly higher, narrower,
winding, valley sections of the lowlands are overlooked on
both sides by eroded hills and ridges which extend inland to
the major ranges. The chief westward-flowing rivers, such as
the Kum, Han, Imjin, Yesong, Taedong, and Ch'ongch'on,
also form natural barriers across lines of north ? south move-
ment.
From south to north, the lowlands have been designated
according to the principal rivers, the Kum, the Han, the com-
bined Imjin and Yesong, the Taedong, and the Ch'ongch'on.
The hills and ridges separating the lowlands have been named
according to the provinces where these hills are principally
located. The lowlands have the following characteristics: (1)
They are moderately to extremely winding, and are drained
by very sinuous streams; (2) near the sea they become flatter
and broader (10 to 30 miles) with extensive rice cultivation,
canals, and ditches; (3) the principal rivers empty into estu-
aries 1 to 4 miles wide, where, at low tide, 1 to 5 miles of
slimy mud flats are exposed; (4) the river banks are alternate-
ly steep and gentle; the lower hills are locally terraced and
cultivated; the steeper and higher hills are gullied by erosion,
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and are pattly covered with grass, scrub pine, and scattered
trees; (5) the lowland areas are intensively cultivated; rice
is the principal crop and is grown chiefly in the lower parts;
dikes, some of which are 15 to 20 feet high, protect the cud-
tivated fields from flood waters; (6) hills or ridges overlook
every part of these lowlands; concealment is generally lack-
ing in the lowlands as well as in the hills; (7) the most favor-
able routes for cross-country movement on these lowlands are
in or near the low, rolling hill sections; these routes are very
winding, but have few bottlenecks, and generally have ample
room for deployment.
The principal north ? south road and rail routes and im-
portant east ? west routes join in the Han Valley at Seoul,
which is the transportation hub of the peninsula. From this
place road and rail routes go northeast to Wonsan, south-
east to Pusan, south to Taejon, west to Inch'on, and north-
west to P'yongyang and Sinuiju. Taejon, in the Kum Valley,
and P'yongyang, in the Taedong Valley, are also situated at
road and rail junctions. From each of these cities routes lead
north ? south and east ? west.
(f) Wonsan -- Seoul Corridor. The Wonsan ? Seoul Cor-
ridor trends nearly north ? south through the east coast
mountains and separates the Northern Taebaek Range from
the Southern Taebaek Range. It is followed by a road and
rail route about 60 miles long. Near the northern and southern
ends of the corridor, the rail route follows gently sloping
valleys a mile or more in width. The middle 12 miles of the
rail route is in a narrow gorge or depression. Highest eleva-
tions on the rail route are about 2,000 feet. The road route is
longer and has a maximum elevation of about 2,300 feet.
The northern and southern parts of the road route are similar
to the rail route, but the middle 30 miles goes through alter-
nately wide and narrow stream valleys, bordered by steep
hills. Both routes have a steep portion a mile or two long.
Although the corridor is not entirely suitable for rapid, large-
scale movement, it offers less difficulty than other east ? west
routes.
B. Drainage and water supply (FIGURES I - 15 to I - 17).
Korea is well watered and well drained. It has an intricate
drainage network but relatively few lakes. Marshes are small
and of only local significance except in coastal tidal areas.
(1) Rivers.
There are nine principal river systems, each of which has an
extensive drainage basin.
(a) Major rivers. The Tuman-gang is the only major
eastward-flowing stream of Korea. It drains most of north-
eastern Korea and flows into the Sea of Japan. Its lower course
is navigable by lighter craft for about 50 miles. The lowest
10 miles of its course separates the Maritime Province of Si-
beria from Korea. Its upper section forms part of the boundary
between Korea and Manchuria.
The Naktong-gang and the Somjin-gang flow southward
and are the principal rivers in southern Korea. The Naktong-
gang is navigable by light craft for about 200 miles.
On the west side of the Korean Peninsula are the Yongsan-
gang, Kum-gang, Han-gang, Taedong-gang and the Ch'ong-
ch'on-gang systems, all of which drain into the Yellow Sea.
These streams are comparatively long, very sinuous, and have
extensive tidal flats at their mouths.
In the northwest, the Amnok-kang forms part of the bound-
ary between Manchuria and Korea and flows southwestward
into the Yellow Sea. The Amnok-kang is 500 miles long and
is Korea's longest river. It and its tributaries have cut deeply
entrenched, narrow, winding valleys with relatively flat bot-
toms. Its main channel is encumbered by many islands and
'sand banks in the lower course and by numerous upstream
rapids. The river is navigable by small, light craft, such as
motor boats, for about 350 miles up from its mouth.
(b) River characteristics. Except for the Amnok, Korean
rivers are short (100 to 350 miles). Generally, they are swift
in their upper courses, slow in their middle reaches, and ex-
cepting those along the eastern coast, have built up fairly large
flood plains. With m [nor exceptions the pattern of drainage
trends with the relief of the peninsula. A common character-
istic is the very large amount of debris carried by the east
coast streams and in the upper reaches of all streams. This
results in boulder-filled channels in the swift sections and sedi-
ment-loaded water throughout. Few of the rivers could be used
as waterways but their valleys are important as routes for
movement.
The main rivers range in width from 4 miles (at the mouth
of the Amnok-kang) to about 50 yards (in the narrow gorges
of the upper Tuman-gang). Normally, most of the major rivers
are 1/4 to 1/2 mile wide at many points. Many smaller streams
range between 100 and 200 yards in width.
Most Korean streams are relatively shallow. Many of the
river courses are fordable during low-water season (November
to March). Their average normal depth is 2 to 3 feet in their
upper reaches and about 6 to 9 feet in their lower courses.
During high-water season many of the streams become raging
torrents, and flash floods occur. The amount of debris trans-
ported is enormous; the rivers raise their stream beds and
Hood the valley bottoms downstream. At such times flood
waters 5 to 15 feet deep may inundate the rice fields. During
highwater season the rivers would be a major barrier to
movement.
In their lower courses, especially near the west and south
coasts, the streams have low banks. The banks of the lower
Nak tong-gang and of the streams along the west coast are
10 to 15 feet high. Many of the upper courses of the streams
flow through narrow valleys with cliffs 30 to 50 or more feet
high. Numerous rock gorges of the upper Amnok-kang and
Tuman-gang (and of the short streams along the east coast)
are more than 100 feet deep. Generally, the river banks of
the lowland areas are of sand and gravel and are gradual in
slope. Many of the banks have long barren stretches inter-
rupted by patches of grass and thickets. Along many of the
stream banks are large boulders and rocks moved downstream
during high water.
The rivers in northern Korea are frozen from 3 to 4 months
annually. Those in the central sections of the peninsula are
frozen from 2 to 3 months. During winter many of the streams
and irrigation canals in the Western Lowlands are frozen and
can be crossed by foot troops. The rivers and streams of south-
ern Korea, however, are open all year.
(2) Lakes and marshes.
There are no large lakes or ponds in the peninsula. Two
large reservoirs have been constructed in the Northern Korean
Highlands, and the very large Sup'ung Reservoir is in the
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Amnok Valley. There are many small ponds and lagoons scat-
tered along the east coast, but these are mainly of only local
significance. Small marsh areas are numerous locally, especially
along the tidal river mouths of the west and south coasts.
Generally, they can be by-passed and are only minor barriers
to movement.
(3) Water supply.
Korea has a plentiful supply of water in most sections of
the peninsula. It is not safe for consumption and should be
treated before use. The water table is high along the coast
most of the year and much of the water tastes brackish. Many
of the larger towns have water supply systems but most of
the rural population obtains its supply from wells. Owing to
the lack of vegetative cover, and to mountainous terrain, run-
off is rapid. The amount of water available varies with the
season and location. Rainfall normally averages 35 to 40 inches
annually. The heaviest fall occurs in the southeast, south, and
west; the north and northeast are slightly drier and their rain-
fall is less variable. Abundant winter snows in the mountains
help maintain summer runoff to lowland areas. Fall and win-
ter are the dry periods.
C. Soil trafficability (FIGURE I - 18).
Soil trafficability is the capacity of soils to support vehicles
moving cross country, or on unimproved roads or trails. Soil
trafficability is determined by soil type ( textural grade, organic
matter content, and other profile features) , topography, vegeta-
tion, and weather factors. In this area the important weather
factors are precipitation (duration, intensity, and character ) ;
temperature ( as it affects evaporation, plant growth, and the
freezing and thawing of soil); and wind, cloud cover, and hu-
midity, which affect evaporation of soil moisture.
(1) Terrain and soil trafficability.
By far the greater part of Korea is rough or mountainous
and therefore unfavorable for cross-country movement of
wheeled vehicles, regardless of soil or weather conditions.
Where topography is favorable in valley and coastal low-
lands, much of the land is planted to wet rice. Rice paddy
lands are particularly numerous in southwestern Korea where
great irrigation projects have extended a complicated net-
work of canals over the valley and coastal plains. The paddy
lands are flooded and nontrafficable from early June until the
harvest during October or early November. After the harvest
most of the paddy fields north of 37 ? N are fallow, but canals
(which in many places are raised above the general level of
the fields) and irrigation ditches remain serious obstacles to
cross-country movement. South of 370 N, winter crops are
raised in some fields on ridges about 1 foot high and 2 feet
wide, spaced about 21/2 feet apart; these ridges are additional
obstacles to cross-country movement. The areas in which
mountain lands and lowland rice paddy land predominate are
shown on the soil trafficability map (FIGURE I - 18).
In nonpaddy areas of favorable topography, soil drainage
characteristics and weather factors are particularly important
in determining the feasibility, route, and rate of cross-country
vehicular movement. In such areas medium-textured soils
(loams) , many of which are stony or gravelly, arc the most
common textural type. Where these soils occur on valley ter-
races or hill slopes, they remain trafficable during nonpersistent
light or medium rains. During heavy or persistent rains, how-
ever, they become slippery and muddy and may mire vehicles
locally. Their normal trafficability is regained rapidly after
periods of rain. Loams occurring in lowland areas will mire
vehicles almost everywhere during heavy or persistent rains,
dry rather slowly, and are locally subject to flooding by stream
overflow.
Fine-textured soils (clay barns and clays) also have wide-
spread distribution in valley lowlands, on terraces and low hill
slopes. The clay soils are slippery and muddy when wet, and,
other factors being equal, they require a longer period than do
loams to regain trafficability after periods of rain. In northern-
most Korea, the clays are frequently peaty types which hold
moisture and afford poor trafficability except when deeply
frozen.
Coarse-textured (sandy and gravelly) soils afford the most
favorable all-weather trafficability conditions. Where these
soils occur on beaches or narrow coastal strips, they are traffic-
able at most places regardless of weather conditions. The
tides along the western and southern coasts range up to 30
feet and extensive coastal flats are exposed at low tide. Where
these flats are sandy, they may support light traffic, but traffic-
ability deteriorates rapidly with continuous passage of vehicles.
The coarse-textured soils in inland areas are trafficable at most
places except during heavy rains or following persistent rainy
periods. They are subject to local flooding in stream valleys.
The soil trafficability map (FIGURE I - 18) indicates in as
much detail as is possible on such a small scale, the areas
where the different soil types predominate. The legend is self-
explanatory insofar as it indicates the relative trafficability of
the different soil types in their natural state. Caution is urged
in the use of the map, however, as it shows general regional
contrasts only, rather than detailed information for any one
place.
(2) Weather and soil trafficability.
In Korea as a whole, the most favorable period for the
cross-country movement of wheeled vehicles is during late
September, October, and early November. During this period,
precipitation is generally light and infrequent at most places,
and paddy lands are drained for harvest. Precipitation is further
decreased, both in amount and frequency, for the period from
late November through February, but there are important
regional contrasts in trafficability. In coastal lowland areas
south of 37 ? N, where a snow cover seldom persists, general
trafficability may be better during winter than during the fall.
Shallow soil freezing may occur for a few days at a time but
the periods of thaw which follow do not seriously reduce
trafficability.
Northward from 37 ? N, winter trafficability for wheeled
vehicles becomes less favorable because of a more persistent
snow cover. There are few data on the depth of snow, but, in
coastal regions, it probably seldom exceeds a foot on level low-
lands. In northwestern Korea, several feet of snow are com-
mon in drifts in inland valleys and on westward slopes. Soil
freezing is usually persistent from December through Febru-
ary in inland areas north of 37 ? N, and is probably deep
enough to aid vehicular movement where the snow cover is
light or absent. In coastal areas soil freezing is less persistent,
and periods of surface thaw cause poor trafficability during
the winter. Most streams and rivers north of 38 ? N freeze over
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during late November or December in a normal year, and
the ice will probably support vehicles of light and medium
weight at most places during January and February.
During March and April the soil is often saturated, and
trafficability is generally poor. Soil moisture provided by melt-
ing snows and thawing soil drains slowly, because of the dis-
ruption of normal soil drainage channels by the winter freez-
ing. Stream ice also breaks up at this time. Trafficability con-
ditions are much more favorable in southern Korea than in
northern Korea during this period.
During May and early June rains are frequent but light at
most places.; although the lowland soils and clay soils are
frequently slippery and muddy, the soils with better drainage
properties ate usually trafficable.
During tl_e period from late June through early September,
heavy and persistent rains produce periods of widespread poor
trafficability: A large proportion of the annual precipitation
falls during. this period which is the least favorable, in most
of the area, for cross-country movement of wheeled vehicles.
Additional details concerning the climate of each terrain re-
gion are included in PLAN 3.
D. Vegetation (FIGURE I - 19 and PLAN 3).
The most significant features of Korea's vegetation pattern
are the treeless, grass-clad hills and mountains which are
found almost everywhere throughout the peninsula. Low scrub
pine is scattered over mountain slopes. Cultivated areas are
concentrated in the valleys. Some small local areas have been
reforested. Only in sections of the Northern Korean High-
lands and within large monastery domains in the Southern
Taebaek Range, has the forest been little disturbed. There,
large native forests remain. These original forests are the ex-
ceptions, for in more than 2/3 of the whole country the natural
tree growth has been destroyed. Where no cultivation is at-
tempted and in crop areas that have been abandoned, coarse
grasses, shrubs, and scrub pine dominate. Wood is the chief
fuel in Korea; the trees and shrubs are hacked and maimed
annually to supply firewood. As a result, the forest is most
seriously depleted in areas of the most dense population. Tree
types are similar to those of the New England States. Such
trees as pine, fir, spruce, oak, birch, and maple are most
common.
There are 5 major vegetation types in Korea. There are (1)
the mixed deciduous* broadleaf and coniferous forest, (2)
deciduous broadleaf forest, (3) cultivated area, (4) barren
sections, and (5) marsh lands. Grasslands are associated with
all types.
(1) Mixed deciduous broadleaf and coniferous forest.
The mixed forest includes almost of the forested area
of Korea. Pine and fir are the two most common coniferous
trees in this forest. Red pine grows in all parts of Korea ex-
cept on the highest mountains and in the cold northern in-
terior. Oak and birch are the common broadleaf trees. Most
of the mixed forest has been cut over at least once, and the
present trees are second growth. Much is bush forest of low
quality. In the Yangnim Mountains of the Northern Korean
Highlands, and in the Southern Taebaek Range some red
pines are 75 feet tall and 3 to 4 feet in diameter. In the
mixed forest, flat-leaf spruce, Korean fir, and nut pine may
* Deciduous trees are those that lose their leaves in winter.
be from 80 to 120 feet tall and from 3 to 5 feet thick. Oaks
and birches are sometimes 50 to 60 feet tall and from 2 to 3
feet in diameter. Within the repeatedly cut-over sections of
the region, these trees are much smaller. In some mountain
sections a gradual transition from mixed forest to pure conif-
erous forest occurs, usually at between 4,000 to 5,000 feet
elevation. Coniferous forests predominate on the northern
slopes of Cheju-do, and on other high mountains. There are
few mountains that extend above the tree limit. The important
exception is Paektu-san. The trees are low and deformed near
the upper limit of tree growth. In the mixed forests of the
'north, tree growth ceases at an elevation of about 6,000 feet.
In the extreme southwestern part of the peninsula and on
Cheju-do there is, below the mixed forest zone, a narrow
'strip of broadleaf evergreen forest including bamboo.
Generally, the undergrowth in the mixed forests is only
moderately dense. It varies with the stage of forest develop-
Ment in any given locality. In the secondary forest of pine,
fir, oaks and maples on the plateau of the Kanan-san (Region
4: Northern Taebaek Range) at an elevation of 4,800 feet,
the forest is so thick that it may require 11/2 hours to go 1,500
feet. In older forests, there is an abundance of tree trunks and
low limbs covered with vines. Such a forest surrounds Paektu-
San for a considerable distance. Generally, passability increases
With altitude. The coniferous forests of red pine are easier to
penetrate than the mixed forest at lower elevations. The ex-
tensive larch forests of northeastern Korea are relatively clear
of underbrush. (Larch is a deciduous conifer.)
The summits of higher mountains are covered with alpine
Shrubs, such as creeping pine, dwarf juniper, and dwarf willow
;in great variety.
(2) Broadleaf forest.
Broadleaf forests are most extensive in the northwestern
part of the peninsula. Smaller areas parallel the northeast
!coast and are scattered throughout the Northern and the
...Southern Taebaek Ranges. Oak, birch, maple, aspen, willow,
'poplar, and elm are the most common broadleaf trees. Among
the largest ones in the natural forest are the Mongolian Oak
!which may be about 60 feet tall, and 2 to 3 feet thick. A
'common species of birch sometimes grows to about the same
!size. The small-leaf elm may develop to about 75 feet in
iheight and 3 to 5 feet in thickness. Forests of these trees are
most common to steep, rocky mountains unsuited to agricul-
ture, where the soil is poor and there is little settlement near-
by. In general, broadleaf trees of Korea are not large when
!compared with similar species in forests in America, Europe
or Japan. In contrast to the mixed forests, the ,broadleaf forests
;have a dense undergrowth. Shrubs and vines grow in abun-
dance. Flowering species include azalea, rose, magnolia, honey-
Suckle, lilac, forsythia, and spiiraea.
(3) Cultivated areas.
Approximately 20 percent of the 85,000 square mile area
iof Korea is cultivated. Korea is a land of varied climate, and
correspondingly varied crops and crop practices. In winter the
fields of southern Korea are green with barley or other grains
while snow lies deep in the northern interior.
i The cultivated areas have their largest extent in the Western
!Lowlands and Hills ( Region 10) , but the entire peninsula is
;intensively cultivated wherever possible. In all the more acces-
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sible valleys, slopes, and plateaus the most fertile soils have
been brought under cultivation. Paddy rice is by far the prin-
cipal crop and occupies l/3 of all the cultivated land. Other
crops, in addition to various small grains, include soy beans,
potatoes, corn, grain sorghum, cotton, fruits, low growing
vegetables, and ginseng. From North P'yongan to South Cholla
Provinces, the populous centers are in the wide, intensively
cultivated valleys. In the lower mountain regions, patchy agri-
culture of wheat, millet, and barley predominates, and even
in a few of the mountain valleys rice cultivation is attempted.
Cultivation in Korea is divided into two essentially different
types approximately along the 37th parallel of north latitude.
To the south, winter crops are grown on the rice fields. To
the north, there is no double cropping. Depending on the re-
gion and locality, rice is generally planted in seed beds in
April and transplanted into the fields in early June. Harvest-
ing occurs during October. In the south, where fields are used
for double cropping, the rice fields are replanted in October
to another crop, such as beans or grain, which is harvested
usually in June, and the field is then replanted with rice. Fields
where double cropping does not occur remain idle during the
winter season. There is more irrigation in the south than else-
where.
Much of the cultivation in the mountainous regions is char-
acterized by cultivated lands cleared by fire, called kaden (liter-
ally fire fields). Permanently cultivated fire fields extend up to
elevations of 4,000 to 5,000 feet and are found even on steep
slopes. They are most extensive in the Northern Korean High-
lands and on the forested slopes of mountains marginal to
lowlands. The burned-over areas are rectangular in shape.
Generally, more forest burns than is needed. Stumps are left
standing and are from 3 to 9 feet high. These tree stumps and
tree trunks lie between the rows of cultivated plants. In
winter the fire-cleared fields stand out as white spots on a gray
background; in spring, brown on a green background. In the
summer and fall the colors of the field will depend on the crop
and stage of advancement, bright green, greenish-white, yellow,
yellowish-brown, or wine-red. After a few years the field is
abandoned and becomes covered with grass, bushes, and weeds.
If the soil has not been eroded too much, a poor growth of
secondary forest may cover the field.
(4) Barren sections.
Areas lacking a vegetative cover are found throughout
Korea, particularly in the Western Lowlands and Hills (Re-
gion 10) and in the Naktong Basin and Hills (Region 7 ) .
These barren areas are scattered along the valley flood plains,
often interrupted only by patches of grass. In places, the barren
sections may extend along the rivers for several miles. In other
areas they are small, and intermingled with scattered trees or
irregular cultivated fields. There are also numerous barren
rock ledges and outcrops along the steep and narrow valley
sides and on the steep mountain slopes.
(5) Marshlands.
There are many marsh and swamp areas throughout the
peninsula. They are most numerous near the tidal river mouths
along the west and south coasts, but do not include the exten-
sive tidal flats of the west coast. Small in extent, they could
usually be by-passed. Two of the largest marsh areas are near
the Pujon and Changjin Reservoirs in the North Korean High-
lands (Region 3).
(6) Effect of vegetation on operations.
In general, relief interposes much greater hindrances to
movement than does vegetation. In forested areas, the foliage
usually offers good concealment. Numerous sections of the
peninsula can be penetrated without encountering dense under-
brush. Kaden, or fire fields, numerous stumps and high tree
trunks offer partial concealment for small groups of men. In
cultivated areas, most crops are low growing, and excepting
the wet rice fields, in western and southern Korea offer no
hinderance to cross-country movement. In the western and
southern coastal regions, wood for fuel or construction pur-
poses would be difficult to obtain.
E. Significant areas (FIGURE I - 20).
Six areas in Korea have particular significance, in that they
are situated at or near a natural passageway, through a natural
barrier, or a junction of main routes. Control of these areas is
probably essential to success of military operations in their
vicinity. These areas are as follows:
1. Northeastern Korea, especially Ch'ongjin, Najin, and Unggi.
2. Wonsan area.
3. Wonsan ? Seoul Corridor.
4. Pusan area.
5. Seoul (Kyongsong) area.
6. Sinuiju ? An-rung area.
F. Routes to significant areas (FIGURE I - 20).
The two chief routes of Korea are:
1. Pusan to An-rung?approximately 550 miles.
2. Seoul to Tu-men?approximately 560 miles via coastal branch,
510 miles via inland branch (Hoeryong). This route branches
from the Pusan ? An-rung route at Seoul.
There are several alternate routes. One of these extends
from Chonui to Mokp'o, at the southwestern extremity of the
peninsula. Other alternate routes are:
Taegu to Suwon, running east of Route 1.
P'yongyang to Wonsan, connecting Routes 1 and 2.
Anju to Manp'ojin, an alternate approach to Manchuria from
Route 1.
The chief routes and alternate routes named above are de-
scribed in considerable detail in the ROUTE SUPPLEMENT.
In addition to these routes or comprising parts of them, are
numerous regional routes. These are shown in FIGURE I - 15
and are described in Topic 22 of Chapter II.
3. Oceanography
The waters of Korea are characterized by: (1) moderate
to large tides on the south and west coasts, (2) strong tidal
currents at times, and (3) in certain areas thin ice and slush
which may occasionally become a hindrance to navigation.
A. Regional considerations.
Along the east coast of Korea the tidal range is small, and
the daily variation in water level due to the weather is often
greater than that caused by the tide. Along the south coast
there is a mean tidal range of 3 to 8 feet, with tropic tidal
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ranges as great as 11.5 feet. Along the west coast and among
the offshore islands, the mean range varies from 2 to 21
feet, with a maximum at springs of 27.5 feet. Along the
shores of Cheju-do (Saishii-to, Quelpart) there is a mean
range of 25 to 5.5 feet and a spring maximum of 7.5 feet.
At Tsushima the mean range is 3 to 5 feet, and the spring
maximum is 6.5 feet. The tides are semidiurnal, but there is
usually a diurnal inequality when the moon is near its north
or south declination.
The tidal currents are weak and irregular off the east
coast, but they are often strong in the passes between the
islands off the south and west coasts. Moderate tidal currents
are experieaced near Cheju-do (Saisha-to, Quelpart) and Tsu-
shima. The tidal currents are semidiurnal in character but,
like the tides, they may have a noticeable diurnal inequality
when the moon is near its north or south declination.
The oceanic currents are important only along the south
coast and the southern part of the east coast of Korea where
the oceanic drift flows eastward north of Cheju-do (Saishd-to,
Quelpart), northeastward through Korea Strait, and finally
northward parallel to the east coast of Korea. This drift has
an average velocity as high as 15 miles per day.
Off the east coast of Korea sand and sand and mud occur in
most of the bays and coves with rock between the bays and off
headlands. Seaward the shelf is usually mud, but in the south
part and off the south coast, mud and sand and mud grade
into sand in the middle of Korea Strait and in the Yellow Sea.
Off the west coast, rock predominates in the southern part, but
it is replaced by sand and sand and mud farther north.
B. Seasonal considerations.
Along the east coast of Korea there is a monthly variation
in water level of more than 1 foot on the average. The water
is lowest in April and highest in August.
Low seas are most prevalent from May through August,
and high seas are commonest from October through March.
Seas from north or northwest prevail from November through
March and 'prom southwest or south from May through August.
Swell greater than 6 feet in height is improbable at any time
in the Yellow Sea, but off the east coast of Korea swell 8 to
10 feet high may occur on 2 to 4 days per month from Sep-
tember through February.
The mean sea surface temperature varies from 360 to 60?
F. in winter and from 700 to 80? F. in summer. Extremes
of 31? and 86? F. have been recorded in this area. Thin ice
forms in sOme ports on the east coast of Korea for as long
as 4 months during the year, and thin ice and slush, which
may obstruct navigation, sometimes occur off the west coast
late in JanUary and early in February. The mean temperature
of the water is 1? to 9? F. warmer than that of the air from
September through May and 1? to 5 ? F. colder during the
remainder of the year.
Average echo ranges on a submarine at periscope depth vary
from 500 yards in summer to 2,750 yards in winter; in spring
and fall average ranges are usually less than 1,000 yards. The
best depth for evasion for a submarine is at periscope depth in
spring, summer, and fall; in winter, ranges are approximately
the same at all depths.
4. Coasts and Landing Beaches
(FIGURE - 21)
A. East coast.
Approaches to the east coast of Korea, between the mouth
of the Tuman-gang (Toman-ko or Tuman Ula) and Sungdu-
mal (Yoto-matsu or Harito Kutsu), are mainly clear; there
are only a few small off-lying islands and shoals. Bottom gradi-
ents commonly range from steep to moderate except for the
southernmost 40 miles, where they are more gradual. Most of
the bottom consists of mud and sand with occasional rocky
patches; sand predominates in most of the bays and coves.
The coast is fairly regular; it consists of low, level sandy
,stretches alternating with stretches of slopes and cliffs. Where
' the low, level stretches are closely spaced, Wide beaches are
almost continuous, but along the mountainous sections beaches
mostly are confined to sandy pockets at the heads of coves. The
? beaches are exposed to heavy seasonal surf; few approaches are
channeled; foreshore slopes average approximately 1 on 75;
the beaches average 75 to 100 feet in width. Five beaches or
groups of beaches in this sector are described in detail in the
text (beach areas (14 ), (50), (62), (114); and (125) ); all
these are located at the heads. of fairly large bays and in the
vicinity of ports.
The slopes and cliffs are backed by steep hills or rugged
.mountains, and the beaches by alluvial plains that terminate
a few miles inland at the mouths of deep, narrow valleys.
.Within 20 miles or less of the coast, mountains rise to heights
of 4,000 to 6,000 feet.
Vegetation on the uplands consists chiefly of a mixture of
grass, brush, scrub pine, and scattered pine trees. The alluvial
.areas are cultivated in irrigated rice and grain.
B. South coast.
The approaches to the south coast, between Sungdu-mal
(Yoto-matsu or Harito Kutsu) and Haenam-gak (Kainan-
kaku), are obstructed by numerous off-lying islands and islets,
and by rocks, reefs, and shoals. Most of the approaches to the
outer islands and islets are relatively clear. TWO large islands,
Tsushima and Cheju-do (Saisha-to or Quelpart Island), lie
off the eastern and western extremities of the south coast, re-
spectively; they are separated from the mainland and its off-
lying islands by channels 30 to 40 miles wide.
Bottom gradients are irregular, and range from steep to flat.
Along the greater part of the coasts of both the mainland and
the islands, however, the gradients are steep to moderate.
Off the hilly or mountainous stretches, the bottom near shore
consists of a mosaic of rock, gravel, sand, mud, and shells; off
the alluvial stretches it is composed of mud or sand with patches
of shells. Seaward, the bottom materials grade into mud with
local areas of sand or shells.
The coast is irregular, consisting of long peninsulas alternat-
ing with deeply indented bays. Much of the coast, particularly
along the bays, is fronted by drying tidal flats, ranging from
narrow to broad, composed of mud or sand.
Cliffs and slopes of varying degrees of steepness, backed by
bills or mountains, make up most of the coast. The cliffs and
.slopes generally rise directly from the water's edge, but in
Many places, particularly at the heads of the coves, they are
!fronted by narrow beaches. At varying intervals, the hilly or
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mountainous parts of the coast are broken by low, level, sandy
or muddy stretches which range in length from a few hundred
feet to several miles. These stretches front alluvial flats or
plains; where the coast is muddy, diked salt pans or earth em-
bankments may border the shore. The largest river plains lead
inland from the heads of the principal bays.
The only described beaches in the area are beach area (181) ,
near Yosu (Reisui), and beach area (217) , near Mosulp'o on
Cheju-do. Most of the beaches are protected from heavy surf;
approaches are generally channeled; foreshore slopes average
1 on 200 or flatter; the beaches are fronted by wide drying
flats, and average 25 to 50 feet wide.
The mountains which back the coast and surround the al-
luvial plains are highest in the eastern part of the sector, and
become progressively lower westward; they are steep and rugged
throughout. The mountain slopes are cut by numerous short,
steep, narrow ravines.
The coasts of Tsushima are mainly steep and cliffy, but
there are numerous pocket beaches, mainly at the heads of
indentations where streams have formed small alluvial flats.
The coasts of Cheju-do (Saishil-to or Quelpart Island) are
more regular in outline than those of Tsushima, but are al-
most entirely steep and rocky; of the few beaches on Cheju-do,
the majority are fringed with rocks. The larger of the islands
lying close off the mainland coast have a coastal terrain simi-
lar to that of the mainland, except that extensive river plains
are lacking; the smaller islands and islets consist of hills or
mountains terminating in cliffs.
Vegetation on the upland areas of both the mainland and
the off-lying islands and islets consists principally of a mixture
of grass, brush, and scrub pine and other coniferous trees.
Stands of broadleaf trees are present in places, particularly on
Cheju-do. Some of the lower, gentler hill slopes are cultivated.
The alluvial flats are planted chiefly to irrigated rice or grain.
Deciduous orchards occur around most of the villages.
C. West coast, southern and central parts.
The western coast between Haenam-gak (Kainan-kaku) and
Changsan-got (Chansan Kotsu) is very irregular both in out-
line and in offshore gradient. The approaches are encumbered
by broad shoals, detached banks, and numerous archipelagos.
Channels leading through the islands and shoals are narrow,
difficult, and in many places shallow. The shores, both of the
mainland and the numerous islands, are generally fronted by
broad mud flats which fill most of the inlets and in places ex-
tend two or three miles from the coasts. Stretches of sand flats
along the outer edge of the tidal mud flats are common.
The coast of this sector generally consists of slopes and oc-
casional stretches of cliffs, which are broken at intervals by low
alluvial flats. Sandy beaches appear in places but they are usu-
ally small and fronted by mud flats. The beaches are similar
in physical character to those on the south coast. Only two
large described beaches lie in this sector (beach areas (243)
and (288) ). Cultivation along the coast consists almost en-
tirely of irrigated rice fields and these are confined to narrow
coastal strips and small valleys. These fields are generally pro-
tected by dikes, and in some places sections of the tidal mud
flats have been reclaimed for cultivation. Salt pans are com-
mon along the shores of the inlets.
The terrain back of the coast is generally hilly. Low hills
predominate, but more precipitous slopes rising to elevations
of 500 to 800 feet are also common, and there are some peaks
of 1,000 feet or more. The lower slopes of these hills are
grassy, with many patches of scrub pine growth. The higher
hills usually have a cover of coniferous trees with occasional
broadleaf growth.
D. West coast, northern part.
The nearshore approaches to the west coast north of Chang-
san-got (Chansan Kotsu) generally are shallow, particularly
along the northern part. They are obstructed by many long,
narrow shoals and detached banks stretching in a general
north ? south direction. Many of the shoals and banks are
marked by drying sand bars. Several islands lie off the coast,
particularly in the northern part of the area.
The coast in this sector is varied. Along much of the coast,
hills fall steeply to the sea, and offshore rocks are common.
Elsewhere, there are long unbroken stretches of marsh and
several sandy stretches, particularly in the south. The southern
part of the coast is fronted by narrow tidal sand flats; in the
remainder of the sector, the coast commonly is fringed by
broad mud flats, some of which merge seaward into sand flats.
The coastal plains tend to be somewhat larger in this sector
than farther south, and the hills on the promontories and back
of the coast generally are steep and somewhat higher. The
beaches are similar in physical character to those on the south
coast. No beaches in this sector have been described in detail
in the text.
The alluvial flats and the rugged stretches of the coast are
backed by hills and mountains in which elevations of more
than 1,000 feet are common. Cultivation in the valleys and on
the coastal plains is largely limited to irrigated rice. Cover on
the uncultivated plains and on the hill slopes is generally grass
and scrub pine, with some sparse growth of other coniferous
and broadleaf trees.
5. Climate and Weather
Korea, on the eastern borders of the continent of Asia,
has a climate which is largely continental in character in win-
ter, when the principal air streams flow out from high pres-
sure over the continent of Asia toward lower pressure off
the Asiatic coast, and largely maritime in character in sum-
mer, when the prevailing air streams are from the Pacific across
the coasts toward lower pressure in the interior of Asia. As a
result, the winters are relatively dry and cold and the sum-
mers are moist and hot. The contrasts between winter and sum-
mer are extreme, and year-round residence requires adjustment
to the severely cold weather of the Asiatic winters and the
"hothouse" climate of the tropic-like summers.
A. Storms.
Cyclonic disturbances seldom affect Korea in the winter
months, but are quite common in the spring and early summer
months. Several types affect the peninsula. Storms which sweep
far to the north over Siberia have trailing cold fronts which
bring unsettled weather and rain to Korea, and, occasionally in
the spring, widespread dust from the deserts of Mongolia and
north China. Other disturbances cross Korea directly from
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124 126 128 130
1 1 1
44
421
AVERAGE
?
JANUARY
:
PRECIPITATION
LEGEND
MORE THAN
2.0 INCHES
LESS THAN
.
I
44
, 0.5 INCH
42
IN
.. %
..
.-
40
.----r-'?':-
co 0

40
38
1 .
f.
.,
38
36
D
I.
,
. ? ?
A.?
0 ? 0
o 9 8
V
36
34
34
gielW
qZ)
A
C\
124 126 128 130
124 126 128 130
1 1 1 1
44
AVERAGE PRECIPITATION
JULY
? LEGEND
?44
4
-
MORE THAN
16 INCHES
LESS THAN
.?F.'
. (7"
j.
4 INCHES
42
i
... q
? .? ,
1.0?
1
i I .. :i.?
i
40
38
a
: .. . ...
ii
t
r
CI
38
36
34
D
.!:.
,
cz
C4.I 0 OD
0 0
61
36
:tit
n eIl
,
124 126 128 130
FIGURE I - 6. Pi.ecipitation.
Average precipitation for January and July.
orrential rains, winds speeds of 75 to 150 m.P.h. or more, and
by very high "following tides" which cause immense damage
along windward coasts.
B. Precipitation.
Mongolia and Manchuria. Wave disturbances form on fronts
quasi-stationary in the Hwang-Ho region and cross the Hwang
Hai (Yellow Sea) directly to Korea, causing widespread rains.
Other fronts that become quasi-stationary over the Yangtze
Valley develop waves which have an adverse effect on the
weather in southern Korea. At other times the polar front may
become quasi-stationary across Korea in summer, attended by
general rains over the peninsula, even though cyclonic dis-
turbances do not form on the front. A northward extension of
the intertropic front, very diffuse and evident only as a zone
of convergence, may also lie across Korea in midsummer and
may be attended by heavy rains.
Typhoons may be expected to affect Korea on the average
of twice a year, their period of occurrence being limited to the
period 1 June to 15 September. Typhoons are very severe
storms which effectually stop operations of all types during
their passage. They are attended by widespread low overcast,
Mean precipitation in Korea varies between approximately
20 inches in the northeast along the upper reaches of the
Tuman-gang and nearly 60 inches along the south coast in
the vicinity of Sunch'on (FIGURE I - 11). Over most of the
peninsula the annual precipitation varies from slightly less
than 40 inches to more than 50 inches, the lesser amOunts
occurring along the northwest coast in the vicinity of P'yong-
yang and over the smaller islands off the west coast, and the
larger amounts, in the more mountainous interior. At Izuhara
on the neighboring islands of Tsushima, as much as 90 inches
is normal.
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Confidential
Approved For Release 2006/09/25 : CIA-RDP79-01144A000900010001-1
BRIEF
Page I - 17
124 126 128 130
I I I I
44
PERCENTAGE OF THE
TOTAL PRECIPITATION
OCCURRING IN
WINTER
- LEGEND
?44
Fi ?
MORE THAN
10 PERCENT
LESS THAN
5 PERCENT
I.
I-
42?
42
40?
V
40
o
38
.
..,
38
36
a
gr.
a 00
0 0
..
:
.0
36
34
4"
ti
(11
ts\
34
124 126 128 130
124 126 128 130
I I I 1
44-
PERCENTAGE OF THE
TOTAL PRECIPITATION
OCCURRING IN
SUMMER
LEGEND
?44
..1 ?,
4
'"
MORE THAN
60? F.
LESS THAN
400 F.
t
?
...
42
-
...
42
40
?
. ?
o
o
40
36
a
0
Ot,
o o
ca
38
q ot
_
1...
1> .
o o
36
34
69
tIn
124 126 128 130
FIGURE I - 7. Precipitation.
Percentages of precipitation in winter and summer.
The seasonal distribution of precipitation is very striking
(FIGURE I- 7). Approximately 85% of the annual amount of
precipitation falls in the period April through September. The
winter precipitation is very light, varying between less than
an inch monthly in the interior to slightly over 2 inches month-
ly along the southeast coast. Winter precipitation is most fre-
quent along the southwest coast and over the more mountain-
ous islands. Moderately heavy precipitation occurs on Ullung-
do, where snow, or occasionally rain, falls 5 of every 6 days
in winter. During spring and summer the amount of precipi-
tation in Korea increases rapidly until July, when it reaches a
maximum. Total amounts for July vary from 4 or 5 inches
in the drier valleys of the northeast to 12 to 14 inches in locali-
ties in the west and south near the mountains. In rainy years
18 to 25 inches are not uncommon amounts to be received at
these stations.
Snow may occur anywhere in Korea in the winter months,
but the total amount is so small that depths of more than one
foot are not to be expected except on Ullung-do and in interior
valleys, where the snow is blown off the adjacent mountains
into the valleys.
C. Temperature.
Winter temperatures are severe in northern Korea, with
mean minimum temperatures consistently below zero, and ex-
treme minima of ?30? to ?40? F. (FIGURE I - 8). In January,
the coldest month, there is a difference of 40? F. in the
average temperatures between Chunggangj in in the extreme
north-central part of Korea and Mokp'o on the southwest coast.
In the latter place minimum temperatures average a few de-
grees below freezing, with extremes between 50 and 10? F.
Summer temperatures throughout Korea are consistently high,
but not extreme (FIGURE I - 9). At low-level stations the av-
erage summer temperatures are between 75 ? and 80? F. in
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Page 1- 18
Approved For Release 2006/09/25 : CIA-RDP79-01144A000900010001-1
BRIEV
Confidential
44
, 124 126
AVERAGE DAILY
MAXIMUM TEMPERATURE
JANUARY
' LEGEND
MORE THAN
45?F
128 130
1
?44
42
LESS THAN
15? F
4P
40 ?
40
38
313
36
36
34
34
124 126
("\
128 130
124 126 128 130
44
42
40
38
36
34
44?
12?
4 0
I 1
.......
III
'44
Pi ?
! f-
0
, '' .?:N!
?
MINIMUM
AVERAGE
JANUARY
LEGEND
DAILY
TEMPERATURE
MORE R0E THAN
3
LESS THAN
?I 5?F?
ON
.,
All
?
00
to "
o
.ti
a 0
38
1
36
34
i
!,
o D
4-
.
05 00c
o
i
ti , 0
).,?,.;,:',. .
.
.
0
0.
128
i l IL
A
130
124 I 26
FIGURE I - 8. Temperature.
Average daily maximum and minimum temperatures for January.
the warmest month, with average maxima between 830 and
88? F. and extreme maxima near 100? F.
D. Humidity.
Relative humidities are moderate throughout the cooler
months of the year but are consistently high in midsummer
(FIGURE I -: 10 ) . The moderate humidities of the cool season
do not impctse any particular problem in relation to military
operations, but the high humidities of the summer require
special precautions to prevent the spoilage of foodstuffs, the
corrosion of petals, the molding of leathers and other fabrics,
and injury to technical instruments.
E. Surface winds.
In a country as mountainous as Korea, surface winds tend
to be greatly modified by the local topography and do not re-
flect the gradient wind flow. In the cool season of the year the
prevailing air flow is between north and northwest, except in
the northwestern portion of the country along the Amnok-
hang, where the gradient flow Is between north and northeast.
Strong surface winds blow along the southwest coast, where
the winds have had a long sweep over the waters of the
Hwang Hai (Yellow Sea), and along the northeast coast,
where they flow direct ly from the cold interior to the warmer
sea surfaces of the Japan Sea. Very light winds are the rule
in protected valleys of the interior. In the spring and fall
months downslope (foehn) winds from the mountains of the
interior to the coasts of the Japan Sea are quite frequent. This
condition arises whenever a deepening cyclonic disturbance in
the adjacent portion of the Japan Sea is associated with rising
pressure over the mountains of Korea. The foehn winds are
attended by high temperatures and very low humidities. They
are particularly noticeable in the vicinity of Wonsan. In sum-
mer, both wind direction and wind speed are extremely van-
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Confidential
Approved For Release 2006/09/25 : CIA-RDP79-01144A000900010001-1
BRIEF
AVERAGE DAILY
MAXIMUM TEMPERATURE
Pagel- 19
124 126 128 130
I I I 1
44?
AVERAGE DAILY
MINI MUM TEMPERATURE
JULY
LEGEND
?44
42?
. ,..0
MORE THAN
LESS THAN
65? F
/
/
i .
42
I
If
40?
38
o
0
:
Ai?
40
36
, tt
0 6
C2
38
34
15'.
1
'o .-,
00
64 tO0 0 0
lb ?
-t.
?
g9
0
36
f
OP
ci)
0
rv
c't
34
124 126 128 130
FIGURE I - 9. T emperatuire.
Average daily maximum and minimum temperatures for July.
able. Wind roses for a south coast and a west coast station are
given in FIGURE I - 11.
F. Winds aloft.
Winds aloft in the cool season of the year are from the
northwest in the lower levels, backing to west with increasing
elevation. Very high wind speeds are to be expected at times
because of the steep pressure gradients which occur aloft over
Korea. In summer the winds aloft are variable up to 10,000
feet, with westerly winds prevailing above that level. Very
high winds are not to be expected at ordinary flying levels in
summer.
G. Cloudiness.
Cloudiness in the winter months varies largely with the
location of the station, i.e., whether or not the prevailing winds
over the station have been modified by long trajectories over
the adjacent seas. Where the trajectories of the prevailing
air flow have been entirely over land, the skies are predominant-
ly clear. This is the case in northern Korea, where the average
cloudiness in the winter months is 30 to 40%. Where the
trajectories of the prevailing air flow have been over the Hwang
Hai (Yellow Sea) or over the Japan Sea, overcast conditions
with stratocumulus clouds are common. This is the case along
the southwest coast of Korea and over the larger islands, with
average cloudiness over the former 55 to 65%, and over the
north coasts of the large islands such as Cheju 80 to 85%
(FIGURE I - 12) . In summer the cloudiness is high throughout
all of Korea, averaging 70 to 80% over most sections. Quel-
part (Cheju-do) has less cloudiness in summer than in winter
(FIGURE I - 13),
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Page 1-20
Approved For Release 2006/09/25 : CIA-RDP79-01144A000900010001-1
BRIEF
Confidential
100
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