In modern military terminology, a frigate is a warship intended to protect other warships and merchant ships as anti-submarine warfare (ASW) combatants for amphibious expeditionary forces, underway replenishment groups, and merchant convoys.
During the age of sail, a frigate was a sailing vessel designed for speed, with a flush gun deck carrying 24 to 44 guns, used as scouts attached to larger fleets, as commerce raiders, for blockade duty, and for the protection of convoys. With the introduction of steam and steel warships frigates as a class of warship passed out of use until World War II when they were reintroduced by the British as an antisubmarine escort vessel larger than a corvette but smaller than a destroyer. Sail frigates and steam frigates evolved into cruisers; they are only related to modern frigates by name.
Perhaps one of Englands greatest shipwrights, Sir Phineas Pett, lived for ten years after the construction of one of the worlds greatest ships, the 'Sovereign of the Seas' was built and launched by his son Peter. Phineas Petts innovations were perhaps to be finally realized in the designs of his son Peter Pett for the Frigate a design of English shipwrightry worthy of Mathew Baker. Sir Peter Pett was almost as distinguished as his father. He was the builder of the first frigate, The Constant Warwick.
Sir William Symonds says of this vessel: "She was an incomparable sailer, remarkable for her sharpness and the fineness of her lines; and many were built like her." Pett "introduced convex lines on the immersed part of the hull, with the studding and sprit sails; and, in short, he appears to have fully deserved his character of being the best ship architect of his time."
In the United States Navy, guided missile frigates (with the FFG hull classification symbol) bring an anti-air warfare (AAW) capability to the frigate mission, but they have some limitations. Designed as cost-efficient surface combatants, they lack the multi-mission capability necessary for modern surface combatants faced with multiple, high-technology threats and offer limited capacity for growth. Until 1975, these vessels were called "Ocean Escorts" and designated "DE" or "DEG" (a holdover from the Second World War, when they were called "Destroyer escorts").
From the 1950s to the 1970s, the US Navy commissioned several "guided missile frigates" (which were actually AAW cruisers built on destroyer-style hulls), some of which (Bainbridge, Truxtun, and the California and Virginia classes) were nuclear. They were far larger than any other frigates ever seen, and all were properly reclassified as guided missile cruisers in 1975 (except for the smaller Farragut-class ships, which were reclassified as guided missile destroyers) and struck from the Naval Vessel Register in the 1990s. USS Long Beach (CGN-9, ex-CGN-160, ex-CLGNGN-160) was the last cruiser in the United States Navy to be laid down on a cruiser-style hull.