World War II
When the U.S. entered World War II, the D.C. Guard mobilized immediately. The D.C. National Guard was home to the headquarters of the famed 29th Infantry Division. America depended heavily on the training and experience the National Guard possessed to form the backbone of a military rapidly filling with new recruits and draftees. National Guard units grouped together to train before going overseas to war. The D.C. National Guard’s 121st Combat Engineers was among the first units on the beaches of Normandy on D-Day. Other D.C.N.G. personnel fought in the Pacific theater. 
In 1940, the 121st Observation Squadron was organized and began operations out of Bolling Field. At the end of the war, it was merged with the 121st Fighter Squadron, Single Engine, and the 352d Fighter Group, creating the lineage of the 113th Wing. The 113th Wing carries campaign credit from the Antisubmarine Campaign, the Po Valley Campaign, the North Apennines Campaign and the Rome-Arno Campaign.​​​