When is a frigate not a frigate? When is it a Corvette, or a Destroyer, or a Cruiser? Does any one know the criteria for the different classes of warships? Does it relate to the tonnage only, or does the weapons fit come into it?

Until the late 19th century the term frigate used to relate to a fast, medium-sized warship that was used for general tasks like scouting, patrolling and commerce raiding. The term fell out of use and was replaced with "cruiser" which basically covered anything bigger than a destroyer or a torpedo boat but smaller than a battleship or battlecruiser. When the term came back into use in the middle of WW2 it referred to a twin-screw ASW vessel between the size of corvette (which lacked capability) and a destroyer (which was too expensive). After the war the "General Purpose" frigate still roughly kept the ASW emphasis with some offensive anti-surface capabilty (guns and later ASM's) and a self-defence AAW capability (at least in Western Navies), though some frigates from the 1970's like the Oliver Hazard Perry class had more balanced capabilities. The class increased in size from am average of under 2000 tonnes in WW2  to around 4000 tonnes now, though all classes of ships have increased in size over that period so they remain in the same position as . The Europeans seem to be calling their big AAW ships Frigates rather than Destroyers now, though I don't think that it is really an accurate use of the term. I don't know why they do it, its probably because it doesn't sound as nasty ;-).

Ooops, I forgot Corvette, Destroyer and Cruiser.

Corvette - A really fast, cool car .. just kidding. Started off as a small runabout sailing warship and went out of fashion like frigates did, but the name was used again (in between the World Wars I think) to mean a cheap, slow, single screw ASW type of under 1000 tonnes or so. With modern weapons Corvettes have grown to between 1000tonne to 2000tonne and have a balance between ASW and Anti-Surface capabilities and anti-air self defence, but generally only has the range, sea keeping and capability for local type deployments. . Anything smaller than 1000 tonnes is generally considered to be a patrol boat or fast attack craft and usually can only take on one role or another.

 

Destroyer - Fast late 19th century warship of around 1000tonnes designed to hunt Torpedo boats with fast firing guns. Role changed to hunting submarines and taking over the Torpedo boats job of nailing battleships with torpedos. Once the ASW role was increasingly taken over by frigates and with the advent of SAM's the type grew to around 4000 tonnes and tended to be a specialised AAW type in Western Navies (though an Anti-surface type in the Soviet Union). With bigger AAW systems the type grew again into cruiser territory of around 6000 - 8000 tonnes.

 

Cruiser - As I described in the frigate section, Cruisers used to be anything bigger than a torpedo boat or but smaller than a battleship. With the advent of the destroyer, cruisers ranged from around 3000 tonnes to battlecruisers (40,000 tonnes for the Hood) and as destroyers grew in size then cruisers grew as well at the lower end, though shrunk at the upper end. In Western Navies during the Cold War they were generally considered to be large (+ or - 10,000 tonne) vessels with balanced capabilities but with an emphasis on long range AAW systems, designed to protect an aircraft carrier or lead a surface action group. Nowdays destroyers are big and capable enough to do that so there really isn't much distinction apart from the fact that a cruiser might be a bit bigger if any more ever get built. The Soviets/Russians emphasise(d) Anti-Surface warfare in their cruisers with big missiles to attack US CGB's.

Things were more simple in the 60's & 70's were'nt they. We had the Charles F Adams class destroyers, although less than 4'000 tons you could not call them anything else.  Now look at the Arliegh Burke's, at 9'600 tons and still a Destroyer?

My query, a ship of about 2'700 tons today, would it be classed as a Frigate or Corvette?

2. Anti-submarine warfare ship

3. Aviation base ship

4. Amphibious warfare ship

5. Submarine

6. Logistics ship.

 

You can subtype within class for specialist ships and it makes sense. 

1. Anti-air/surface warfare ship