The original frigates emerged in the age of sail as swift warships for patrolling, escorting merchant vessels, and engaging in commerce raiding. They were the smallest ships capable of serving in the line of battle, thus were typically commanded by a post-captain. Unlike the smaller brigs or sloops, the Royal Navy classed frigates in accordance with its rating system.
Fourth-rate frigates were often razed battleships, sporting about fifty guns. The US Navy's Constitution and her sisters could have been classed as fourth-rates, and were regarded as super-frigates. Fifth-rate frigates were more typical, serving as the general purpose warship of their day. These frigates were particularly useful in engaging in what became known as cruiser warfare or commerce raiding. The last rated warships, the sixth-rate frigates performed the less glamourous jobs of escorting merchant ships, blockading enemy ports, and relaying dispatches.
The term lasted until the late nineteenth-century as the world's navies converted from sail to steam, before falling into disuse. The frigate's functions became those of the cruising-ships or cruiser, but the term survived in the rank structure of the French, Italian, and Spanish navies.
During the Second World War, the term came into use once more. The Royal Navy used the term to describe anti-submarine ships larger than a corvette but smaller than a destroyer. After the War, function rather than size governed the classification of such vessels. Destroyers were air defence vessels, while frigates, such as the large Type 22, were dedicated anti-submarine ships.
The US Navy took a different approach. During the 1950s, the Navy classed its guided missile-equipped destroyer leaders (DLG) as frigates. In the late 1960s, the Navy redesignated those large destroyers as guided missile cruisers, re-adopting the term frigate along the British lines for its destroyer escorts (DE), which then became FF.
The French Navy designated its large Suffren-class destroyers as frigates. Tellingly, the ships were alloted cruiser hull numbers.
The ASW function continues in NS navies, but augmented by a somewhat more generalist weapons package and doctrinal use as escort ships. The list of known NS naval frigates include:
- Ardent Class FFG of The Freethinkers
- Bullfinch class FFH of Isselmere-Nieland
- Coalport class FFH of Isselmere-Nieland
- Community Vessel Frigate of Sober Thought
- Furtive class FFH of Isselmere-Nieland
- Phlegethon-class frigate of Knootoss
- Katana Class Light Assault Frigate of Asgarnieu
NationStates space force
Generalisations are more difficult to make in the space force; consult list of known NS space frigates below for details: