Joint Advisory Commission, Korea

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.

Source: Wikipedia — Joint Advisory Commission, Korea (CC BY-SA 4.0)