During World War II, destroyers served essentially the three basic functions they had in World War I: to act as screening ships to defend their fleets from those of an enemy, to attack an enemy's screening ships, and to defend their fleet from submarines. However, there was an increased desire to introduce anti-aircraft measures to the destroyers, although many nations struggled to do so effectively. How destroyers were actually used varied by country. Germany did not use her destroyers to defend against submarines, hence their lack of strong anti-submarine armament. Germany relied on a massive fleet of trawlers that had been requisitioned and refitted as minelayers instead. British destroyers were built for escorting fleets, defending them from enemy planes and sinking submarines. German destroyers were built to escort fleets, or act as torpedo boats. The role of the destroyer began to vary more widely as World War II progressed, with five parallel evolutions: the all-purpose destroyer (all countries), the anti-submarine destroyer (United States and United Kingdom), the anti-aircraft destroyer (Japan and the United Kingdom), the small destroyer (Germany and Italy), and the super-large destroyer (France).
