World War II was where national air forces came of age, where individual planes coalesced into unstoppable squadrons, and where wartime tactics were dictated from the sky down. Germany rained shells down on London, the Allies executed precision bombing raids by day and frightful carpet bombing missions by night. Pathfinders led bomber squadrons to their targets, and fighters protected other planes as they flew. By the time America dropped the atomic bomb, each airplane had its own role.