Essex was a class of aircraft carriers of the Unite States Navy, which constituted the 20th century's most numerous class of heavy warships, with 24 ships built. These included members of the "long-hull" Ticonderoga variant/subclass, which some consider a separate class. Thirty-two were originally ordered, however six were cancelled before construction, and two were cancelled after construction had begun. The Essex-class, along with the three Midway-class carriers, were the backbone of the Navy's combat strength from the later years of World War II, until the supercarriers began to come into the fleet in numbers during the 1960s and 1970s.