Cover Photo: 326th Communications Reconnaissance Company in Korea in 1951 @] @] I UNirEV srArESCRYPrOLO(iIC HisroRY I I� I I Ser�V I I �Earl:}'P<>Stwar Per� 1945-1952 Ii I Volume,3 iI I iI � � � The,Korearv War: I iI I I The,SI<.iINT Background iI � � � � � � � David A. Hatch � � with I I Robert Louis Benson I i � I I �I Ii � i I� �I � � I I I CENTER FOR CRYPTOLOGIC HISTORY I I NATIONAL SECURITY AGENCY I I 2000 I I� If§j @] @] This page left intentionally blank Introduction peripheral areas occupied by Japan. One of the thorniest problems was the status of Korea. Since the revelation of the vital role of cryp­ tology in World War II, the contribution of The peninsula had been an independent communications intelligence (COMINT) and nation forcenturies beforethe Japanese took it communications security (COMSEC) in post­ as a colony in 1910. In August 1945, Soviet war conflicts has become a frequent question forces were fighting the Japanese military on for many, particularly scholars and veterans' the China-Korea border, and it appeared that groups. the Red Army might occupy all of Korea. This short summary of the cryptologic back­ The U.S. solutionwas a temporary division ground to the Korean War is intended to pro­ of the country. Americans would take the vide only a general overview of the conflict Japanese surrender in the southern sector, from a cryptologic perspective and give initial Soviet troops in the north. After a suitable - answers to some of the more important ques­ but undefined - period in which Koreans tions about intelligence support. would be prepared for self-rule, both armies would withdTaw. The Soviets agreed to this This paper has been cobbled together from plan, and Korea was divided on either side of summaries prepared during or immediately the 38th parallel. after the period of hostilities, some original documents, and the memories of some of the However, as the Cold War developed, the participants. Some of the materials on which peninsula became a pawn in a larger, interna­ this history is based may not be declassified by tional ideological struggle. After three years, its publication date (June 2000). I have pre­ the United States turned the problem over to pared the booklet in this unusual manner in the United Nations, which mandated elections order to have a general history in time for the to decide on a unified government in Korea. 50th anniversary of the beginning of the war. UN-sponsored elections led to the formationof the Republic of Korea (ROK) on August 15, This booklet is therefore intended only as 1948, under President Syngman Rhee, with its an introduction to the subject, an interim his­ capital in Seoul. North Korea declined to par­ tory until further declassification allows the ticipate in the UN elections and formed its own fuller history of cryptologic support during the government, the Democratic People's Republic Korean War to be written. I would like to of Korea (DPRK), with Kim II-song as its leader emphasize that much remains to be researched and its capital in Pyongyang. and studied about cryptology in Korea and, in fact, I look forwardto more detailed studies of The next two years were marked by struggle cryptology in the Korean War in the near on many levels - military, political, and ideo­ futuTe. logical. Small unit clashes and armed incur­ sions along the 38th parallel were frequent. The Korean War Both the ROK and the DPRK built military forces, but there was a difference: the USSR When it became clear in mid-August 1945 supplied armor and aircraft to Pyongyang, that Japan intended to sunender, U.S. policy while the U.S. denied them to Seoul. makers began to make arrangements for Page 1 The USSR, as confirmed by the VENONA est feats of American arms ever, an amphibious decrypts, which NSA released to the public in landing behind North Korean lines at the port 1995-97, had stolen the secrets of the atomic of lnch'on. This operation, combined with a bomb through espionage. Without espionage it breakout from the Pusan Perimeter, smashed is inconceivable that the Soviets would have the DPRK's military forces. had their own atomic bomb 1bythe time of the Korean War. Several U.S. and British spies UN forces, primarily American and South were able to keep the Soviets abreast of U.S. Korean troops, crossed into North Korean ter­ and allied diplomatic, military, and intelligence ritory in pursuit of their retreating enemy, activities well into the Korean War period.1 despite warnings from Communist China to remain below the 38th parallel. In November, The United States deliberately excluded as U.S. and South Korean forces approached South Korea from the defensive perimeter it the China-Korea border, the People's was drawing around the Pacific Ocean area. Liberation Army (PLA) struck them in force, The ROK, said U.S. officials, should depend on sending the UN army in a precipitous retreat the United Nations for support. southward. Finally, in the early hours of June 25, 1950, In the spring of 1951, UN forces reestab­ the Korean People's Army (KPA) crossed the lished a stable line of resistance with the com­ dividing line in strength and began pushing munist armies at roughly the midpoint of the southward toward Seoul. After some initial Korean peninsula. Both sides entrenched. The resistance, the ROK Army gave way before the Korean War continued for more than two larger, stronger KPA, and retreat became rout. years, but consisted largely of limited offensive operations, characterized by only small gains President Harry S. Truman and his advisers and losses, to capture or defend particular assumed the USSR had directed the attack and points of real estate. The strongpoints were that this was the opening move in a wider war. designated officially by their height in meters, At that point, the U.S. reversed its policy and but known popularly by colorful or poignant intervened militarily to support the ROK. The nicknames bestowed by the Gis who fought U.S. persuaded the United Nations to call for over them - The Hook, Old Baldy, Pork Chop assistance in repelling North Korea's aggres­ Hill, and Heartbreak Ridge. sion, and a number of other UN members sent troops or supporting forces. Once the lines had hardened, truce talks opened. The negotiations were first held in the After a period of retreat, General Walton city of Kaesong, behind communist lines. This Walker, in command of the U.S. Eighth Army, was unsatisfactoryto the UN side, so the meet­ stabilized the lines around a defensible area ings were moved to Panmunjom, an obscure that came to be known as the "Pusan village in "no-man's land." Perimeter." Deployed largely along the mean­ dering Naktong River, Walker moved his forces The war ended in August 1953, after more quickly and astutely to blunt repeated North than three years of combat, with the signing of Korean attacks. a truce agreement and the exchange of prison­ ers. On 15 September 1950, a USMC/Army amphibious force, spearheaded by Marines, During the war and in postwar investiga­ striking according to General Douglas tions, there were many charges that U.S. intel­ MacArthur's plans, conducted one of the great- ligence had failedin the Korean War, not once, Page 2 but twice. Critics charged that American intel­ SecuTity Group in June 1950. During and after ligence organizations had failed to give warn­ World War II, a portion of Army COMINT ings of the initial North Korean attack in June assets were dedicated to support of the U.S. 1950 and failed again when the Chinese Army Air Corps, and, when the independent entered the war in October 1950. Air Force was created in 1947, these cryptolog­ ic assets were resubordinated to the new Background To U.S. Cryptology organization as the Air Force Security Service (AFSS). In the late 1920s and early 1930s, the U.S. Army and Navy for the first time established Many officials favored centralization of and operated permanent codemaking and cryptologic activities, and in 1949 the codebreaking units. The cryptanalytic units Department of Defense created the Armed expanded at the outbreak of World War II, and Forces Security Agency (AFSA) as a national the enhanced activity paid offin plentiful and organization. AFSA, just by its existence, forced high-quality information on the Germans and the Army and Navy to redefine the organiza­ Japanese - their location, armament, and tion and roles of their cryptologic services. The intentions. Working in close cooperation with cryptologic agencies of all three services began Great Britain, U.S. military and civilian deci­ structuring themselves to provide direct sion-makers got accustomed to detailed inside COMINT support for American fightingforces. information about their enemies (and a few neutrals). It was furthermore intended that AFSA eliminate duplication of effort among the Allied exploitation of the German Enigma Service Agencies and get an economy of scale in machine and other high-level German and research and purchasing. As it turned out, Japanese cryptographic systems is well known. however, AFSA did not have sufficient legal Less known but also invaluable to the war authority to provide central direction to crypto­ effort was U.S. and British exploitation of logic work. front-line systems to provide a wealth of tacti­ cal information on their enemies' activities. Because there had been no advance budget­ ing for AFSA in 1949, its financial needs were These decision-makers expected the same met initially by reductions in the cryptologic inside information after the war, but encoun­ budgets of the armed services.