Fast naval vessel smaller than a frigate .
In the 18th–19th century corvettes were three-masted ships with square rigging and carried about 20 guns on the top deck. Often used to send dispatches within a battle fleet, they also escorted merchant ships. Early U.S. corvettes won distinction in the War of 1812. They disappeared as a class after the shift to steam power in the mid-19th century, but in World War II the term was applied to small armed vessels that served as escorts for convoys . Modern corvettes, usually displacing 500–1,000 tons (454–900 metric tons) and armed with missiles, torpedoes, and machine guns, perform antisubmarine, antiaircraft, and coastal-patrol duties in small navies.