The Joint Advisory Commission, Korea (JACK; Korean: 주한합동고문단) was a U.S. covert operations unit that participated in the Korean War.
Operating under the direction of the Central Intelligence Agency, JACK was responsible for inserting and extracting U.S.-trained Korean agents into North Korea, conducting covert maritime raids along the North Korean coast, and providing escape and evasion support for downed Air Force pilots.[1]
Yong-do Group (영도유격대) based in Yeongdo District, Busan was the main guerrilla unit.[2]