How 'Mistakes Were Made' In 1950
Secret failures of the Korean War
Just hours after North Korean forces crossed the 38th Parallel in a surprise attack on 25 June 1950, a flight of RB-29s in the 31st Strategic Reconnaissance Squadron (see above photo) left Okinawa for Japan. One of these refueled and took off again for an immediate electronic intelligence (ELINT) overflight of the peninsula. “Almost certainly it was the first operational mission by a US plane during the Korean conflict,” writes electronic warfare historian Dr. Alfred Price.
Although the mission did not detect any North Korean radars, it was the beginning of an American approach to war in which airborne electronic warfare (EW) planes are the very first military hardware to arrive in any new theater of conflict, acting as force multipliers for everything that follows.
American forces had very little information on North Korean capabilities in the first days of the war. The US Army had never mapped the Korean peninsula, and because the native place names had all been restored in a surge of nationalist fervor after liberation in 1945, pre-World War maps available to the US Army in Japan were useless.
Postwar demobilization had cut deep. Not only were American forces in the region thin, American policymakers had excluded South Korea from the zone of national interest in the Far East and denied President Syngman Rhee substantial military aid. Regional resources for the Armed Forces Security Agency (AFSA), forerunner to the National Security Agency, were cut by more than half from 1946-1949. America’s “intelligence community” was only just finding its feet after Congress passed and then amended the National Security Act in 1947 and 1949. In 1950, only two people at AFSA were assigned to Korea; the remaining 110 Far East staff were all watching the communist Chinese.
One ASFA station observing Soviet communications overheard them reporting on surveillance of South Korean radio communications. Other stations caught mentions of medical supplies, such as bandages and medicine, being shipped to North Korea. Another AFSA listening post found a North Korean radio station using Soviet Radio procedures. A program to find and record North Korean communications finally started in April, but the signals were not analyzed until after hostilities began.
An Air Force Office of Special Investigations (AFOSI) detachment had access to human intelligence (HUMINT) sources developed by South Korea, but with only two outstations for signals intelligence (SIGINT) and no aerial photography program, it was difficult to follow up on reports. No intelligence integration was possible without more analysts, anyway.
The US Army Far East Command made no effort to get a better picture of events in Korea. Maj. Gen. Charles Willoughby ran his Korean Liaison Office (KLO) from Tokyo in order to stay close to his boss, Gen. Douglas MacArthur. The arrangement left him detached from the situation at the scene and ensured that information forwarded to MacArthur and Washington went through a political filter.
The CIA was the only agency raising alarms. Six days before the North Korean People’s Army (NKPA) actually crossed the 38th Parallel, they reported “extensive troop movements” across the border, as well as the “evacuation of all residents from the northern side of the parallel to a depth of two kilometers; suspension of civilian freight service from Wonsan to Chorwon and reservation of this line for military supplies only; movement of armed units to border areas; and movements of large shipments of ordnance and ammunition to border areas.”
Still, this was not seen as prelude to invasion. No alarms sounded at GHQ in Tokyo. Willoughby forwarded the information to Washington as routine traffic. Distrusting the CIA, MacArthur ignored it.
During these early days of the Cold War, many US policy makers had a monolithic view of global communism. Mao and Kim il-Sung were thought to be subordinate to Joseph Stalin rather than nationalists with their own independent visions of socialism. Truman, who thought North Korea would never attack without Stalin’s permission, did not know that China and North Korea had already received a green light to act on their own initiative while Moscow sat out the war.
Tokyo and Washington both saw what they wanted to see. In his memoir, Gen. Matthew Ridgway admitted that “wishful thinking may have entered into our misinterpretation of the intelligence reports received just prior to the invasion.” North Korean soldiers were held in contempt, the poor readiness of South Korean or American forces only slightly less so.
Even in Seoul, where some few Koreans warned of imminent war, no preparation took place. The Republic of Korea (ROK) army, which knew of troops concentrating on the northern side of the border, did not connect the dots in time. Half the personnel in many ROK units were on leave when the attack began.
Surprise was therefore total. However, the NKPA attack brought the diffuse and irresolute agencies of American military intelligence into sudden and sharp focus on meeting the threat.
Four days after the invasion, AFSA analytic offices in Washington received a full daily shift of hourly traffic reports. Within weeks it was a double shift and AFSA had rededicated 23 analysis positions to Korean intercept. A military network of thirty outstations and their sub-nets that was later determined to be the principal command net of the NKPA.
Within a week of the invasion, AFSA had identified a military network of 30 outstations and their sub-networks. It was the principle command net of the NKPA. By this means, AFSA identified the entire NKPA order of battle and the G-2 (intelligence section) at Eighth Army headquarters in Korea could track the movements of every unit in the attacking army down to their logistical timetables.
Much of this information was gleaned from traffic analysis, but poor North Korean communications security (COMSEC) practices were also helpful. “The North Koreans were actually sending highly classified materials, like battle plans, in the clear,” Jill Frahm writes in “So Power Can be Brought into Play: SIGINT and the Pusan Perimeter,” a declassified historical essay for the NSA school of cryptology.
When the North Koreans did bother to encrypt communications, it did not matter. As an anonymous source explained to writer Clay Blair for his monumental history The Forgotten War, the NKPA changed their encryption pad every week, but then “it only took one day to break it, then we could read NKPA traffic for four or five days running.” As a result, “Throughout July and August, every major enemy attack was known in advance…” Documents declassified beginning in the year 2000 confirm that NKPA COMSEC was subject to swift and total defeat.
In June of 1950, AFSA had no Korean-language dictionaries or typewriters. A frantic nationwide search found some dictionaries, but the typewriters had to be custom-built. Although not all Chinese and Russian activity could be ignored, assets were re-tasked. “In the two weeks after the start of the war, the number of intercept positions collecting North Korean traffic increased from two to twelve: two Air Force positions, one Navy, and nine Army,” David Hatch and Robert Benson write in another declassified history.
Neutralizing North Korean air power was another priority mission. American forces accomplished it with dispatch. Air Force RB-29s located enemy air power concentrations at Pyongyang and Yonpo through SIGINT, and then US Navy aircraft from the Valley Forge hit both sites while the planes were on the ground. Suddenly, UN forces had air supremacy within two weeks of the war beginning.
Six weeks after the invasion began, the US Army had erected an entire intelligence apparatus focused on Korea. AFSA headquarters in Washington received hourly SIGINT reports from six hundred people working in shifts to exploit the traffic gathered by twelve listening posts. This is how Eighth Army G-2 recognized two NKPA corps coming at them from different directions at Pusan in August.
The attacks on four different fronts were not coordinated, allowing Walker to use his interior lines and reinforce one point at a time. Although Blair recognizes the role of SIGINT as a “priceless asset” for Maj. Gen. Walton Walker, the Patton protégé commanding Eighth Army, somehow it does not explain Walker’s “magical” ability to divine enemy intentions, or why his “limited offensives” from the Pusan perimeter perfectly matched the NKPA movements towards them.
They were spoiling attacks, and they worked, for they brought North Korean progress to a halt on 21 August. Ammunition was low, bridging equipment had to be delivered, and their maps of the Taegu area were insufficient for the NKPA to proceed. Unit dispositions changed as they were reassigned to specific missions outlined in detailed radio instructions. This second wave broke through and even forced Walker’s headquarters to relocate, but still the perimeter held thanks to timely intelligence.
On 5 September, North Korean signals indicated serious logistical problems. Steel bridge locations had given away their axes of advance. Now ASFA intercepts began to reflect a change in morale. “Premier Kim il-sung warned his generals that the longer they delayed in capturing Pusan, the more difficult it would become,” journalist Edwin Hoyt wrote. “The failure of the North Korean Army to break through the US and ROK lines in the first three weeks of August created an atmosphere of desperation in the North Korean camps. Every general knew that his career was on the line, and several had already been sacrificed because of their ‘failures.’”
No amount of broadcast browbeating could fix the basic problem, however. Two months of combat had exhausted the North Korean forces. Their Soviet-supplied army was as the far end of a logistical train that American air power interdicted with increasing ferocity. After MacArthur’s famous Inchon landings in mid-September, the NKPA abandoned their positions around Pusan and fell back all the way to the Yalu river with UN forces in pursuit. ASFA continued to track North Korean units. Some of them went silent, either disintegrating or forming guerilla bands in the mountains as they retreated.
To Tokyo and Washington, it seemed the war was all but won. They were wrong.
Once again, American intelligence did pick up scattered signs of Chinese intervention, and again the dots went unconnected because no one wanted to see the picture they formed.
During August, the handful of ELINT specialists still wearing American uniforms took note when a particularly powerful radar set on the Chinese coast — an American-made SCR-270 100-mHz set from the Second World War — went silent. The following month, American ELINT aircraft located the radar set in a new position at Antung on the Yalu river, the northern border of Korea.
To an air power expert, it sure looked like Chinese intervention was imminent. “The report on the radar's relocation was widely circulated,” one official US Navy history reads, “and although the move was only one indicator to be considered, it should have generated some follow-up collection effort to determine the reason for the move.”
But there was no follow-up. The same mistakes were being repeated, indeed they were being reinforced. Soldiers of the ROK and Eighth Army were about to pay another blood price for the strategic blindness of decision-makers far away from the battlefield.