The 336th Fighter Squadron was constituted by the War Department on 22 august 1942, and was activated at Bushey Hall, England, on 12 September. It had been designated as No. 133 (Eagle) Squadron, and was made up of American volunteers to the Royal Air Force. They were transferred to the US 4th Fighter Group, based at Debden Aerodrome, England, and they were known as "The Rocketeers".

The squadron flew Spitfires until American P-47 Thunderbolts became available in sufficient numbers to equip the group in 1943. A year later the group was re-equipped with P-51 Mustangs, which became the standard until the end of the war.

The 336th Squadron was credited with the destruction of 358 enemy aircraft. The group was deactivated at Camp Kilmer, New Jersey, on 10 November 1945 after the war's end.