Naval warfare
Naval warfare takes place on the high seas (blue water navy). Usually, only large, powerful nations have competent blue water or deep water navies. Modern navies primarily use aircraft carriers, submarines, frigates, cruisers, and destroyers for combat. This provides a versatile array of attacks, capable of hitting ground targets, air targets, or other seafaring vessels. Most modern navies also have a large air support contingent, deployed from aircraft carriers. In World War II, small craft (motor torpedo boats variously called PT boats, MTBs, MGBs, "Schnellboote", or MAS-boats) fought near shore. This developed in the Vietnam War into riverine warfare (brown water navy), in intertidal and river areas. Irregular warfare makes this sort of combat more likely in the future.