An aircraft carrier is a warship designed with a primary mission of deploying and recovering aircraft, acting as a seagoing airbase. Aircraft carriers thus allow a naval force to project air power worldwide without having to depend on local bases for staging aircraft operations. They have evolved from wooden vessels used to deploy ballonns into nuclear-powered warships that carry dozens of fixed wind and rotary-wing aircraft.
Aircraft carriers are typically the capital ship of a fleet, and are extremely expensive to build and important to protect. Of the nine nations that possess an aircraft carrier, six possess only one. Twenty-one aircraft carriers are currently active throughout the world with the U.S. Navy operating 11 as of June 2011.
From foreground to background: HMS Illustrious, USS Harry S. Truman, and USS Dwight D. Eisenhower
The 1903 advent of heavier-than-air, fixed-wing aircraft was closely followed in 1910 by the first experimental take-off of such an airplane from the deck of a United States Navy vessel (cruiser USS Birmingham), and the first experimental landings were conducted in 1911. On 4 May 1912 the first plane to take-off from a ship underway took place when Commander Charles Samson flew from the deck of HMS Hibernia. Seaplane tender support ships came next; in September 1914, the Imperial Japanese Navy Wakamiya conducted the world’s first successful naval-launched air raids. It lowered four Maurice Farman seaplanes into the water using its crane, which were taking off to bombard German forces and could be retrieved back from surface afterwards.
The development of flat top vessels produced the first large fleet ships. In 1918, HMS Argus became the world’s first carrier capable of launching and landing naval aircraft. Carrier evolution was well underway in the mid-1920s, resulting in ships such as HMS Hermes and IJN Höshö. Most early aircraft carriers were conversions of ships that were laid down (or had served) as different ship types: cargo ships, cruisers, battlecruisers, or battleships. The Washington Naval Treaty of 1922 affected aircraft carrier plans. The U.S. and UK were permitted up to 135,000 tons of carriers each, while specific exemptions on the upper tonnage of individual ships permitted conversion of capital ship hulls to carriers such as the Lexington-class aircraft carriers.
During the 1920s, several navies began ordering and building aircraft carriers that were specifically designed as such. This allowed the design to be specialized to their future role and resulted in superior ships. During World War II, these ships became the backbone of the carrier forces of the United States, British, and Japanese navies, known as fleet carriers.
The aircraft carrier was used extensively in World War II, and several types were created as a result. Escort aircraft carriers, such as USS Bogue, were built only during World War II. Although some were purpose-built, most were converted from merchant ships as a stop-gap measure to provide air support for convoys and amphibious invasions. Light aircraft carriers built by the US, such as USS Independence, represented a larger, more “militarized” version of the escort carrier concept. Although the light carriers usually carried the same size air groups as escort carriers, they had the advantage of higher speed since they had been converted from cruisers under construction. The UK 1942 Design Light Fleet Carrier served the Royal Navy during the war and was the hull design chosen for nearly all aircraft carrier equipped navies after the war until the 1980s.