The Cold War Turns Hot

The Korean peninsula, like Poland and the Rhineland, has been the victim of its place on the globe for centuries. The “land of the morning calm,” as it is traditionally known, has often found itself at the center of conflicts between China, Japan and Russia. The few short years after the end of WWII were no exception. After the surrender of Japan in 1945, a hastily-put-together agreement directed Japanese forces north of the country’s 38th parallel to surrender to the Russians.

Those south of the line were to surrender to the Americans. As was the case in postwar Europe, the Soviet Union moved quickly to establish a communist dictatorship in its area of influence. This spur-of-the-moment agreement settled nothing and led to several armed clashes between North and South Korea from 1948 to 1950. During this time, massive amounts of Soviet military hardware were funneled to the North, the majority of which was clearly suited for offensive operations. By the decade’s end, the balance of power had shifted to the North.

Reaction and Retreat

On 25 June 1950, in an attempt to unify the peninsula on their own terms, the North struck across the 38th parallel in a series of well-orchestrated attacks. The South Korean army, with practically no air or antitank capability, was no match for the Soviet-manufactured T-34 tanks and North Korean infantry. By the end of the first week of the war, 40,000 South Korean soldiers had been killed, captured, or declared missing in action. On 27 June, President Truman, supported by a UN resolution, announced that he was ordering U.S forces to support the South Koreans. Three days later, he appointed General Douglas MacArthur commander of the UN forces, and authorized him to commit ground forces to the conflict. Korea had been a mere afterthought for many of the policymakers in Washington. Up until the time of the attack, the troubled nation had been considered outside of the newly established defense lines of the Cold War. The first units to be committed consisted of several U.S. divisions under MacArthur’s command, which had been pulling occupation duty in Japan. Going to war was the last thing they were expecting. Once on the ground they found themselves facing a well-equipped and well-trained adversary. Despite their best efforts, one defeat followed another. The North Korean war machine continued to roll south, with the now-realistic goal of driving the coalition forces off the peninsula for good.

The Fight for Pusan

By month’s end, the North Korean offensive had forced the U.S. 8th Army into a defensive position 50 by 90 miles long, surrounding the vital port of Pusan. The area quickly became known as the “Pusan Perimeter.” The action provided some brief relief from the July onslaughts, but 8th Army commander General Walton H. Walker’s situation was extremely tenuous. Despite the difficult position of his forces, he was committed to holding the line and avoiding a Korean version of the defeat of the Allies at Dunkirk in 1940. In that engagement, Hitler’s Blitzkrieg had forced the remnants of the British Army to the French coast and forced them to flee back across the English Channel. But Pusan would not be another Dunkirk. Like many past American commanders in critical situations, Walker would have the twin resources of effective signals intelligence (SIGINT) to assist him in making the right moves in keeping the perimeter secure and sound communications security (COMSEC) to protect his own communications from being exploited.

After WWII, huge portions of the U.S. government’s war-making machinery were cut back to a bare minimum. U.S. SIGINT activities, despite their proven usefulness, did not escape these budget reductions. In 1949, in an effort to cull the most benefit from the remaining resources, all three military cryptologic services were centralized under the new Armed Forces Security Agency (AFSA). In addition to AFSA, the Army Security Agency and Air Force Security Service continued to play an important role. Prior to the North Korean attack, at the behest of the policymakers in Washington, AFSA and its partners focused almost exclusively on the Cold War challenges posed by the Soviet Union and China. Their justified preoccupation with the communist threat prevented them from properly covering secondary targets, to include Korea. At the time of the 25 June attack, there was only one traffic analyst working on North Korean communications. AFSA had no Korean typewriters, books on the Korean language, nor Korean dictionaries. After the attack, however, the cryptologic community began to rise to the challenge. By October, Korean intercept positions had been increased from two to twenty-three. By late July, enemy intercepts were being processed on a 24-hour basis and crucial North Korean command and control networks had been identified.

Even with the renewed effort by the post-WWII SIGINT community, General Walker faced a difficult, if not impossible, challenge. The conditions within the perimeter at the time were best illustrated by the comments of PFC Leonard Korgie of the 34th Infantry, “When we got into the…Perimeter, you never saw a more beat-up bunch of soldiers…the North Koreans had hellish numbers and equipment. We were very, very thin in both.” (Donald Knox, The Korean War … An Oral History, 1st ed. [New York: Harcourt Brace Jovanivich, 1985], 77)

The Vital Role of SIGINT and COMSEC

The lack of appropriate resources made Walker’s job difficult, but the information from SIGINT proved to be a great equalizer. From the beginning of the siege, Walker had been provided with valuable information such as the exact locations of North Korean positions and detailed information on enemy airfields and general enemy air strength. In mid-August a strange calm fell across the battlefield. Intercepts indicated that the North was regrouping and rearming its forces. Obviously, an enemy offensive was in the works. By the end of the month, the North Korean attacks had resumed with a vengeance. At one point the perimeter was briefly breached, forcing Walker to move his headquarters from Taegu to Pusan. During this crucial time, Walker continued to frantically shuttle his units from one embattled location to another. Aiding him in this desperate situation were detailed enemy intercepts that provided crucial information on the North Korean Army’s capabilities and plans. With this priceless information, Walker was able to determine North Korean intentions and commit his embattled forces with maximum efficiency.

In addition to the precious resource provided by SIGINT, American strategic-level communications during the operation remained safe from the enemy. As was the case in WWII, this was due largely to the dependable SIGABA device, which continued its impeccable record in keeping American plans and intentions from the enemy, and tools such as the M-204, a tactical device that kept U.S. battlefield communications secure.

During the early difficult days of the battle, Walker had firmly remarked to his 25th Division staff, “I want everyone to understand that we are going to hold this time. We are going to win.” Thanks to the dogged determination of the UN forces, and effective SIGINT and COMSEC, Walker would remain true to his words.

“We Shall Land at Inch’on”

On 15 September, MacArthur, despite strong opposition from advisers, conducted a brilliant amphibious landing at the port of Inch’on. Landing well behind North Korean lines. The combined U.S. Army and Marine units involved in the operation delivered a decisive and crushing blow to the enemy offensive. During the same period (September 15-27) Walker’s 8th Army seized the opportunity and broke out of its embattled position within the perimeter to join the attack. North Korea was now on the defensive. Through the use of SIGINT, the coalition forces tracked the haphazard retreat of enemy forces. Operations were going so well that some predicted that the war would be over by Christmas.

This was not to be the case. In October, massive numbers of Chinese infantry smashed across the Yalu River, throwing the UN forces once again on the defensive. It would be three long years before the hostilities would cease. In the end, the opposing nations found themselves in exactly the same place they had been when the conflict began.

Despite the lack of a total victory, Pusan and the events that transpired during that difficult summer serve as constant reminders of the worth of SIGINT and COMSEC in time of war. Pusan was only one of the many battles fought during the conflict, but the actions of those who held the line during that difficult time will always serve as a stark reminder of the bravery and dedication of the individuals who fought and died for freedom in “the land of the morning calm.”

by Patrick D. Weadon

Patrick Weadon currently serves as curator for the National Security Agency’s National Cryptologic Museum, and is only the third curator in the museum’s history.