Destroyer leader (DL) was the United States Navy designation for large destroyers from 9 February 1951 through the early years of the Cold War. United States ships with hull classification symbol DL were officially frigates from 1 January 1955 until 1975. The smaller destroyer leaders were reclassified as destroyers and the larger as cruisers by the United States Navy 1975 ship reclassification; so destroyer escorts could be reclassified as frigates (FF) in conformance with international usage of the term.
By the end of World War I the destroyers intended to screen formations of battleships had evolved to a displacement of approximately 1,100 tons armed with four 4-inch (10 cm) guns and six or more torpedoes.Italy had built three Mirabello-class esploratori (scout cruisers) approximately 70% larger than contemporary destroyers. The Washington Naval Treaty encouraged United Kingdom satisfaction with its traditional fleet of V and W-class destroyers and United States contentment with similar Wickes and Clemson-class destroyers, while the signatories with smaller fleets explored alternative warship configurations between the classical definitions of destroyer and cruiser. Italy launched three more Leone-class esploratori and France responded with six Chacal-class contre-torpilleur super destroyers. Japan launched the minimum light cruiser Yūbari followed by the Fubuki-class special type destroyers 特型 (Tokugata?) with endurance to escort the Kido Butai mobile force of aircraft carriers over the wide reaches of the Pacific.