The radar was intended to be introduced in late 1943, but delays meant the SCR-584 did not reach field units until early 1944. They began replacing the earlier and more complex SCR-268 as the US Army's primary anti-aircraft gun laying system as quickly as they could be produced. They proved easier to use in the field than the less advanced Canadian/British GL Mk. III radar, and many SCR-584's were rushed to England where they were an important part of the defences developed to counter the V1 flying bomb. By the end of the war they had been used to track artillery shells in flight, detect vehicles, and reduce the manpower needed to guide anti-aircraft guns.