A frigate is a small surface ship in the navy that generally has a displacement of more than 500 tons, but is lower than destroyers and cruisers. The main task of the frigate is to provide escort, anti-submarine, anti-air, anti-ship and other combat support for other ships, as well as to carry out coastal patrols, rescue, anti-terrorism and other tasks.
The development of corvettes was influenced by history and reality. Historically, frigates came into being during World War II, when a large number of frigates were built to counter the German submarine threat, often armed with sonar, depth charges, torpedoes, and artillery, to protect merchant ships and transport fleets. After the war, with the withdrawal of battleships from the stage of history, the reduction of cruisers, the expansion of destroyers, and the corresponding increase in the tonnage of frigates, they began to be equipped with more advanced radars, missiles and other equipment for performing more diverse tasks.
From a practical point of view, the development of corvettes is constrained by the strategic needs and economic capabilities of various countries. On the one hand, the United States and other major powers need to build larger and more powerful frigates to meet the needs of operations in the far seas due to the need to maintain maritime security and interests on a global scale. For example, the American Constellation-class frigates have a displacement of more than 7, 000 tons, are equipped with the latest missiles, radars and electromagnetic guns and other systems, which can perform a wide range of tasks and even replace some of the functions of destroyers. On the other hand, small countries such as Iran, due to external sanctions and pressure, do not have enough resources and technology to build more advanced frigates, so they can only be satisfied with smaller and simpler frigates to meet the needs of coastal defense. Iran's Jamalan-class frigates, for example, have a displacement of only 1, 500 tons, are equipped with relatively backward missile, radar and artillery systems, and can only perform limited tasks, if not compete with destroyers.
To sum up, the frigate is a kind of surface ship developed according to the different needs of different countries, and its tonnage varies greatly, but in the future development trend, the tonnage of the frigate is developing towards large-scale, which is to adapt to the complexity and diversity of maritime operations.