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.
Frigates were perhaps the hardest-worked of warship types during the age of sail. They scouted for the fleet, went on commerce-raiding missions and patrols, conveyed messages and dignitaries, and filled in places in the battle-line if there was a shortage of battleships, although more usually they would fight in small numbers or singly against other frigates. They were masterpieces of engineering and design. Their armament ranged from 22 guns on one deck to 74 guns on two decks, making some frigates practically battleships. Common armament was 32-44 long guns, from 8- to 24-pounders, plus a few carronades, which weren't counted in the rating of the ship. In the early steam age (1840-60) steam frigates were the fastest ships around, finally evolving into the cruisers of the 20th Century.
Sail and early steam frigates are only related to modern frigates by name. The name frigates passed out of use until World War II when it was re-introduced by the British to describe an anti-submarine escort vessel larger than a corvette but smaller than a destroyer.
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, Constant Warwick.
Sir William Symonds said 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."
The oldest commissioned warship in the US Navy is the USS Constitution, better known as "Old Ironsides", a frigate launched 21 October 1797 1790s. It is the oldest commissioned warship afloat in the world; HMS Victory, although older, is maintained in drydock. The US Navy's 44-gun frigates (or "superfrigates"), which usually actually carried 56-60 guns, were very powerful and tough. These ships were so well-respected that they were often seen as equal to 4th-rate ships of the line, and RN fighting instructions ordered British frigates (usually 32-guns or less) to never engage American frigates at any less than a 2:1 advantage.
In the late 1800s, the term "frigate" fell out of naval fashion; ships that had been designated frigates were redesignated "cruising-ships" and from there to cruisers. The term "frigate" would lie mostly unused until after the Second World War, when it would be reappropriated to describe ships that during the war had been called destroyer escorts.
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-CLGN-160) was the last cruiser in the United States Navy to be laid down on a cruiser-style hull.
Mississippi was redesignated a CGN before launch and Arkansas was designated a CGN before being laid down; neither served as frigates in the US Navy.
The US Navy altered the designation of the DE (ocean escort) and DEG (ocean escort, guided missile) in June, 1975. The new nomenclature was FF (frigate) and FFG (frigate, guided missile).
The US Navy intends to replace all existing frigates with the Littoral Combat Ship, of which as many as 60 may be built.