ASA operations in Korea began with the first ASA element to arrive in Korea, an eight man detachment deployed in mid-September 1950. They were followed at the end of November by ASA Pacific --Advance (many of whom came from the 126th SSC at Kyoto which shortly thereafter became Field Station 8610 AAU). They absorbed the liaison detachment and took over its mission. The 50th Signal Service Detachment -- COMSEC, relocated from Japan to Korea in early October 1950. At the end of October, the first sizable ASA component, the 60th Signal Service Company from Fort Lewis, Washington arrived in Korea. In June 1951, the 303rd Communication Reconnaissance Battalion arrived and co-located with ASA Pacific -- Advance, as theater ASA command and control. The 501st Communication Reconnaissance Group became operational in July 1951, having been ordered to Korea from Camp Pickett, VA to support the Eighth U.S. Army. The 501st absorbed ASA Pacific -- Advance.
The 501st distinguished itself in the war and, by its end, had participated in six campaigns, receiving the Meritorious Unit Citation of the United States Army and the Republic of Korea's Presidential Unit Citation. As part of a worldwide redesignation of ASA units, the 501st Communications Reconnaissance Group was redesignated as the 501st ASA Group in July 1956. The following year, the 501st was inactivated and replaced by the newly-created 508th USASA Group.
According to an article titled "Vigilance from North to South - The Story of USASA Group Korea." 501st was redesignated as 508th USASA Group in 1957. The article goes on to say that this new name was to last a little more than 10 years and that the group was again officially redesignated as the USASA Group Korea in December 1967."
The actual story of the replacement of the 501st ASA Group by the 508th USASA Group is somewhat more complex. The 501st ASA Group was a TOE (Table of Organization and Equipment) unit while the 508th USASA Group was a TDA (Table of Distribution and Allowance) unit. The difference is at the same time both subtle and profound, and all tied up in the games the military has to play to live within its budget.
The underlying reason for the redesignation lies in the agency having been forced to downsize in 1957. A DoD decision that year cut the Army's strength by 50,000 personnel and threw ASA's force structure into disarray. ASA found itself unable to sustain the manning of its tactical TOE (Table of Organization and Equipment) units.
In order retain a support structure in the tactical commands, the TOE units were inactivated and replaced by units which were tailored specifically to the needs of their supported command (i.e. mission tailored). A company in Korea would be sized and equipped to fit the needs of that theater but would not be structured and equipped the same as a unit, say, in Germany. These new mission structured units were TDA (Table of Distribution and Allowance) units. The designations of these TDA units also differed from the TOE units they replaced. TOE units were designated as "ASA" whereas TDA units were titled "USASA." As a result of these changes, the 501st ASA Group was inactivated and replaced by the 508th USASA Group.
The largest mission of 508th Group was tactical support of the two US combat divisions stationed in Korea during that period, 1st Cavalry Division, located in the Munsan region along the DMZ due north of Seoul, and 7th Infantry Division, located along the DMZ further to the east. In mid-1965, 1st Cav was replaced by the 2nd Infantry Division, which remains today as the only U.S. combat division in Korea. The tactical support function came under 321st USASA Battalion (later re-designated as Det. A, 508th GP) which was headquartered at I Corps headquarters at Camp Red Cloud in Uijongbu.
321st USASA Battalion (successor to the 301st ASA BN) consisted of two operating companies, Company A had its own compound, located adjacent to the town of Yongjukol in the middle of the 1st Cavalry (later 2nd. Div.) area. Company B was located at 7th Division headquarters at Camp Casey in Tongduchon. Company B also had a detachment which had the distinction of being the northernmost ASA unit in Korea. Daily operations for both A and B company consisted of COMINT, COMSEC and some ELINT operations with both the COMINT and COMSEC operations limited to low-level tactical voice intercept and monitoring.
There were two other major operational units subordinate to 508th Group. These were the 277th USASA Operations Company, the 226th USASA Operations Company and the 177th USASA Operations Company . The 277th had its headquarters at the 508th Group compound, with three remotely located platoons. The three platoons were located on PY-do island, Kanghwa-do island and at Sokcho-ri on the Korean east coast. The 226th USASA Operations Company was formed from the 1st Platoon of the 277th when the 277th was eliminated in 1962. The 226th was located on Kanghwa-do Island at the mouth of the Han-Imjin estuary. The 177th USASA Operations Company (successor to the 330th ASA CO) was originally located at Mia-ri at the north edge of Seoul.