In World War II, over 450 members of the Women's Army Auxiliary Corps (WAACs) were assigned to a secret experiment. It called for the creation of coastal gun battery, comprised of both men and women, with the mission to protect the Military District of Washington. Requested by General George C. Marshall, Army Chief of Staff, and dubbed "Battery X", women were mixed into the ranks of the 71st and 89th Coastal Artillery Regiments, thus creating the first-ever composite units. They graduated from the Anti-aircraft Artillery Command school in January, 1943.
The WAACs were assigned to the gun batteries, searchlight units and regiment headquarters. They trained extensively on the 90-mm Antiaircraft Gun M1 and the 40-mm Bofors Automatic Gun M1 (AA). In August, 1943 the experiment was over; women were needed in other areas of service. However, they had proven that if needed Army women could be called upon to serve in antiaircraft units. The story of Battery X was not declassified until the 1970s. Many of their experiences still remain unknown and are yet to be uncovered.