Rugged terrain makes the Korean peninsula a tricky environment for ground-based radio direction finding. Nevertheless, the Army Security Agency (ASA) spun up a substantial signals intelligence (SIGINT) operation in six weeks, proved vital to the defeat of the North Korean People’s Army (NKPA) during October, and then tracked Kim il-Sung as he evacuated his Supreme Headquarters from Pyongyang to Sinuiju on the Manchurian border.
With the enemies of the United Nations now seemingly in full flight, Maj. Gen. Walton H. Walker took time to stop by the ASA company that had set up shop in captured Pyongyang. According to an officer present during the visit, it was the first time Walker had read raw intercept. Until that moment, he had only received the analyzed material in dispatches. Before leaving, Walker asked to receive future intercepts directly, skipping the filters of Tokyo and Washington.
It is possible, indeed probable that Walker did not agree with their assessment of the intelligence. Chinese intervention loomed, and everybody knew it, but Walker was almost alone in respecting the possibility. To his mind, American forces had already invoked Chinese response by crossing the 38th Parallel.
Walker may also have felt shorted of intelligence. His headquarters received very few photoreconnaissance reports . With the vast angle of the northern Korean peninsula widening out before him, Walker worried UN forces were spreading themselves too thin. He was right to worry.
In 1950, the G-2 (intelligence officer) for Far Eastern Command (FEC) in Tokyo had worked for nine years under Gen. Douglas MacArthur, becoming loyal to an actual fault. Brig. Gen. Charles Willoughby developed a talent for telling MacArthur what he wanted to hear.
MacArthur did not think China would intervene, that the window of opportunity for intervention was shut, and anyway if China did attack then the Air Force would stop them with air strikes. All three assumptions were incorrect.
Willoughby’s analysis reflected this disbelief and contempt for Chinese intervention. Rather than check their thinking, President Harry Truman and the Joint Chiefs of Staff (JCS) deferred to the judgment of FEC G-2. Everyone important accepted his wisdom without dissent.
By targeting Chinese civil radio communications, the Armed Forces Security Agency (AFSA) tracked the Chinese Fourth Field Army redeploying from Central China to Manchuria in April and May of 1950. AFSA then reported further troop movements from other parts of China to the Korean border region during September and October while North Korean forces fell back in defeat from Pusan and Inchon.
The Daily Intelligence Summary (DIS) documents FEC G-2 produced during this period are declassified today. SIGINT showed Chinese troops massing on the Korean frontier. CIA reports reflected Chinese war readiness, though they completely misunderstood Chinese war aims. Foreign diplomats warned of Chinese intentions. Chinese newspapers and radio stations actually threatened intervention. MacArthur dismissed it all as “the psychological Cold War.”
Euphoria had set in among American combat troops upon the apparent defeat of the First Wave. The daughter of Col. Percy Thompson, G-2 of a corps command, remembers that his letters home at this time turned pessimistic, as if “he was absolutely sure they were going to be overrun, and he was going to be killed” after his warnings about Chinese forces nearby had been dismissed.
Now reality intruded upon the fantasy and criticism of MacArthur began to grow. “By mid-November, a consensus had emerged that some kind of large Chinese intervention was under way in Korea,” writes military historian Eliot Cohen, “although there was considerable disagreement among American intelligence officials about its scope and purposes.”
Heedless, MacArthur urged his generals to press on all the way to the Yalu, exceeding his orders from the JCS and stretching his logistical tether. Walker felt vulnerable in a hostile landscape where the enemy could hide anywhere. When the hammer blow came, he was the American commander best prepared to “bug out” and preserve the tattered core of his army, forewarned by the intelligence.
The North Korean invasion had been a surprise. The Chinese invasion was not a surprise, but its strength was surprising. In each case, the keystone American policy-maker’s key information filter reflected and amplified his biases.
Korea was not an intelligence priority in 1950 because the possibility of a North Korean invasion was not interesting enough to justify attention from the limited intelligence resources that were available. Then Chinese intervention was not prioritized in American intelligence tasking because the possibility did not interest MacArthur, either.
Walker did not live to claim credit for saving Eighth Army and his reputation suffered from posthumous criticism for “bug out fever.” Yet history has vindicated Walker’s accurate read of the intelligence and his success in saving his command from disaster. Writer and Patton historian Charles Province hails Walker in his biographical title as The Man Who Saved Korea. Perhaps that is saying too much, but it is not too much to suggest that Gen. Douglas MacArthur almost lost Korea.
The war had a lasting legacy on American intelligence. The ASA continued until 1976, when it was subsumed into the new US Army Security Agency. Truman fired MacArthur in 1951 and renamed AFSA in 1952, creating the National Security Agency.
Radio DF teams were dispatched with jeeps and Chinese interpreters to set up remote listening posts and report intercepted dispatches to central analysis stations. These Low-Level Intercept (LLI) teams played a key role in stabilizing the front, then gave early warning of Chinese offensives throughout the bloody years of stalemate until the cease-fire in 1953. SIGINT has been an integrated component of US Army tactical divisions ever since.
Rugged? Try 25% grade hills!