Hard to maneuver galleons of the 16th century, used heavy cannons to blow holes in wooden hulls. Heavy guns replaced cannons at the turn of the 20th century. Torpedoes, exploding shells and cruise missiles are found on today's warships. Today's largest submarines and aircraft carriers are powered by nuclear fuel and can sail for years without refueling. Aircraft carrier Battleship Cruiser Ballistic missile submarine Destroyer Frigate Task forces usually center around an aircraft carrier in groups of about 10.
Convoys are supply ships escorted by armed warships.
Submarines Submarines are designed to operate underwater. The first submarine, invented in 1620, was made of wood and propelled by oars. By 1914, diesel engines and the introduction of torpedoes made the submarine a powerful weapon. The first nuclear submarine, Nautilus, was launched by the U.S. Navy in 1955. Submerged Valves closed Submarines dive and surface by filling and emptying their ballast tanks.