In 1912 Great Britain launched the first airplane from the deck of a moving ship, and Japan launched sea planes in air raids as early as 1914. Within four years the British converted an ocean liner to a flattop carrier of aircraft whose primary purpose was to launch and land airplanes at sea.

By 1922 the United States converted a coaling ship into its first aircraft carrier. The USS Langley (CV-1) was soon followed by the Lexington and Saratoga, two converted cruisers. With these three, America was keeping pace not only with Great Britain, but also with Japan, whose navy covered the western Pacific.

Between the great wars, these three naval powers joined Italy and France to try to limit the size and cost of their fleets. They signed the Washington Treaty in 1922, restricting the tonnage of the battleships, which were still seen as the primary ship of all navies. But carriers, too, were limited by the treaty. The Washington Treaty would survive unchallenged for twelve years. The United States began building the bigger carriers by 1937, and used them in 1941 after the attack on Pearl Harbor.