Helicopter Mine Countermeasures Squadron 12 (HM-12) was the first of its kind. Established at NAS Norfolk, Virginia, on 1 April 1971, the Sea Dragons institutionalized airborne mine countermeasures (AMCM) as a role of U.S. Navy helicopters. HM-12 initially was equipped with CH-53A Sea Stallion helicopters—borrowed from the Marine Corps—capable of towing mine countermeasures sleds. HM-12 was called into action after the 1973 truce in the Vietnam War. The squadron deployed to ships in the Tonkin Gulf, for Operation End Sweep, the clearing of mines from the harbors and coastal waters of North Vietnam. Mission complete, the Sea Dragons returned to Norfolk for transition to the RH-53D version, the first helicopter designed expressly for mine countermeasures.
The use of sea mines in the October 1973 Arab-Israeli War prompted the use of HM-12 to sweep the Suez Canal as part of Operation Nimbus Star and the northern coast of Egypt in Operation Nimbus Stream.
The beginning of the vertical on-board delivery (VOD) role for Sea Stallion helicopters came in November 1976, when HM-12 deployed a detachment to the Mediterranean. The detachment's success was such that RH-53Ds later were assigned full-time to a logistics squadron in the Mediterranean.
This growth resulted in two deployable squadrons being formed in 1978 from HM-12: HM-14 and HM-16. With this growth came the need for a separate fleet readiness squadron (FRS) to train crews and maintenance personnel. HiM-12 gave up its operational role and became the FRS for the airborne mine countermeasures community, as well as those squadrons flying the Sea Stallion in the VOD role.
In 1983, HM-12 acquired its first CH-53E Super Stallion helicopter for training purposes. The RH-53D also was retired in 1987, replaced by the larger MH-53E Sea Dragon. During Operations Desert Shield and Desert Storm (1990-91), HM-12 sent personnel to the combat zone, to augment other HM and HC squadrons.
In a consolidation move, HM-12 was disestablished on 30 September 1994. Its training role was assumed by Marine Helicopter Training Squadron 302 at Marine Corps Air Station New River, North Carolina, and the AMCM Weapon System Training School in Norfolk.