The air warfare of World War II was a major component in all theaters and, together with anti-aircraft warfare, consumed a large fraction of the industrial output of the major powers. Germany and Japan depended on air forces that were closely integrated with land and naval forces; the Axis powers downplayed the advantage of fleets of strategic bombers, and were late in appreciating the need to defend against Allied strategic bombing. By contrast, Britain and the United States took an approach that greatly emphasized strategic bombing, and (to a lesser degree) tactical control of the battlefield by air, as well as adequate air defenses. Both Britain and the U.S. built a strategic force of large, long-range bombers that could carry the air war to the enemy’s homeland. Simultaneously, they built tactical air forces that could win air superiority over the battlefields, thereby giving vital assistance to ground troops. The U.S. and Royal Navy also built a powerful naval-air component based on aircraft carriers, as did Japan; these played the central role in the war at sea.