The squadron was activated at Hamilton Field, California as the 56th Pursuit Squadron on 15 January 1941, It trained with Curtiss P-36 Hawks and Curtiss P-40 Warhawks, then moved to Everett Army Air Field, where it served as a part of the air defense force for the northwest Pacific coast during the first few months of World War II.
The squadron was redesignated as a fighter unit in May 1942.

On 20 June 1942, the air echelon of the 56th took its newly assigned Bell P-39 Airacobras to Nome, Alaska, where it served in combat against the Japanese forces that invaded the Aleutian Islands during the summer of 1942.
  For operations against the Japanese in November 1942 the squadron received a Distinguished Unit Citation.

The air echelon returned to the United States in December 1942 and rejoined the group, which had been assigned to Third Air Force in Louisiana, and became a replacement training unit (RTU) for North American P-51 Mustang pilots.
RTUs were oversized units training individual pilots or aircrews.
In early May 1943, the 54th Fighter Group began a split operation, with headquarters and the 56th and 57th Fighter Squadrons relocating to Bartow Army Air Field, Florida, while the group's other squadron was at Hillsborough Army Air Field.
However, the Army Air Forces (AAF) was finding that standard military units, based on relatively inflexible tables of organization, were proving less well adapted to the training mission.
 Accordingly, a more functional system was adopted in which each base was organized into a separate numbered unit.
As a result, in 1944 the squadron was disbanded as the AAF converted to the AAF Base Unit system.
The units at Bartow were replaced by the 340th AAF Base Unit (Replacement Training Unit, Fighter),
The squadron was activated at Hamilton Field, California as the 56th Pursuit Squadron on 15 January 1941, It trained with Curtiss P-36 Hawks and Curtiss P-40 Warhawks, then moved to Everett Army Air Field, where it served as a part of the air defense force for the northwest Pacific coast during the first few months of World War II. The squadron was redesignated as a fighter unit in May 1942.
On 20 June 1942, the air echelon of the 56th took its newly assigned Bell P-39 Airacobras to Nome, Alaska, where it served in combat against the Japanese forces that invaded the Aleutian Islands during the summer of 1942.   For operations against the Japanese in November 1942 the squadron received a Distinguished Unit Citation.
The air echelon returned to the United States in December 1942 and rejoined the group, which had been assigned to Third Air Force in Louisiana, and became a replacement training unit (RTU) for North American P-51 Mustang pilots. RTUs were oversized units training individual pilots or aircrews. In early May 1943, the 54th Fighter Group began a split operation, with headquarters and the 56th and 57th Fighter Squadrons relocating to Bartow Army Air Field, Florida, while the group's other squadron was at Hillsborough Army Air Field. However, the Army Air Forces (AAF) was finding that standard military units, based on relatively inflexible tables of organization, were proving less well adapted to the training mission.  Accordingly, a more functional system was adopted in which each base was organized into a separate numbered unit. As a result, in 1944 the squadron was disbanded as the AAF converted to the AAF Base Unit system. The units at Bartow were replaced by the 340th AAF Base Unit (Replacement Training Unit, Fighter),
56th Training Squadron