The Japanese Navy was a pioneer in naval aviation, having commisioned the world's first built-from-the-keel-up carrier, the Hosho. Throughout the 1920's and 1930's, they constantly experimented with their carriers, perfecting their design and construction methods, and honing the demanding art of blue-water power projection. They also put in place a tremendously selective and rigorous pilot training program. As a result, by the time Japan attacked the United States, they possessed a fantastically effective naval aviation force, comprised of a core of six large carriers and several more light carriers, whose airwings were manned by long-serving, highly-skilled pilots. For the first six months of the war, this force would roam the Pacific with near impunity, destroying their opponents almost at will. And even well after the debacle at Midway, Japanese carriers and their airwings retained a formaidable punch.