In naval terminology, a destroyer is a fast and maneuverable yet long-endurance warship intended to escort larger vessels in a fleet or battle group and defend them against smaller, short-range but powerful attackers (originally torpedo boats, later submarines and aircraft). Before World War II destroyers were light vessels without the endurance for unattended ocean operations; typically a number of destroyers and a single destroyer tender operated together. During and after the war larger and more powerful destroyers capable of independent operation were built, particularly as cruisers ceased to be used in the 1950s and 60s.
In the US Navy, destroyers operate in support of carrier battle groups, surface action groups, amphibious groups and replenishment groups. The destroyers currently in use by the US Navy are the Arleigh Burke-class. Destroyers (with a DD hull classification symbol) primarily perform anti-submarine warfare duty while guided missile destroyers (DDGs) are multi-mission (anti-submarine, anti-aircraft, and anti-surface warfare) surface combatants. The relatively-recent addition of cruise missile launchers has greatly expanded the role of the destroyer in strike and land-attack warfare. As the expense of heavier surface combatants has generally removed them from the fleet, destroyer tonnage has grown (a modern Arleigh Burke-class destroyer has the same tonnage as a World War II light cruiser). Arleigh Burke is billed by her builders as ton-for-ton the most powerful warship in history.
The Royal Navy currently operates 8 ships of the Type 42 class. The destroyers (as well as frigates) are, as always, the workhorses of the fleet, the former optimised for air defence and the latter for surface and subsurface warfare. They are equally at home in large task groups or on independent operations which may include sanctions enforcement, humanitarian relief or anti-drug patrols. British destroyers (of recent times) have an average displacement of around 5000 tonnes, and are armed with a mixture of guns and missiles including 114 mm (4.5 inch) Mk 8 guns, Sea Dart Missiles, 20 mm Close range guns, Vulcan Phalanx close in weapons system (CIWS), anti submarine torpedo tubes. These ships are due to be replaced by the new Type 45 or Daring Class destroyers which will displace roughly 7,200 tonnes and are predicted to be the most advanced surface warships in the world when they enter service at the end of the decade.
The Canadian Navy currently operates the Iroquois-class destroyers, a class of four helicopter-carrying, anti-aircraft, guided missile destroyers. Launched in the 1970s, the Iroquois's were the first canadian all gas turbine powered military ships, using two turbines for cruise power, and another two fast starting "boost" turbines for speeds of up to 29 knots (54 km/h) (such an arrangement is known as COGOG). Previously the Soviet Navy had used all-gas turbine propulsion on their Kashin class destroyers of the 1960's but the Iroquois were the first to be built to this scheme either on Canada or in the US. The design of the Iroquois was a major inspiration for the US's later Spruance class ships. They were originally fitted out for anti-submarine warfare, but the entire class underwent major retrofits as a part of the Tribal Class Update and Modernization Program, or TRUMP, in the 1990s. These refits had the effect of re-purposing the ships for air-defence, and the ships are now referred to as area air-defence destroyers.
The Russian Navy and the People's Liberation Army Navy of the People's Republic of China operate the Sovremenny class, a class of large multi-purpose missile destroyers. They are powered by pressure-fired boilers, making them capable of speeds in excess of 30 knots. Their armament consists of 8 SS-N-22 Sunburn anti-ship missiles, launchers for SA-N-7 Gadfly anti-air missiles and two AK-130 twin-barreled 130 mm automatic naval guns which can fire laser-guided shells. While they also carry 533 mm torpedo tubes and RBU-6000 rocket launchers for use against submarines, their primary mission is to attack surface ships. Their anti-aircraft missiles have a surface attack mode, and both the 130 mm guns and the torpedoes are useful against ships at close range.
The Indian Navy operates the Delhi class destroyers. These ships are armed with Kh-35 missiles, which have a range of 130 km, in the anti-ship role. These missiles will be replaced by the Brahmos cruise missiles. The Shtil (AKA SA-N-7 Gadfly) system is installed to counter airborne threats. The Barak point-defense missile system has been installed in INS Delhi and will soon be installed in the other two ships of its class. These destroyers also carry the RBU-6000 rockets in the anti-submarine role and are provided with five 533 mm torpedo launch tubes that can launch the SET-65E, Type 53-65 torpedoes. Another strength of these destroyers lies is the capability to carry two Sea King helicopters. The Delhi class will be augmented by the new Kolkata class destroyers, the first of which was launched in March 2006.