A sloop-of-war is a light sailing warship, fitted with a single gun deck and light cannon, typically used for patrols and scouting where contact with larger warships was not expected. Typical armaments included 16-20 guns, but some had up to 28. Sloops were generally assumed to be "ship-rigged", with three masts and square sails, but small seagoing vessels with other rigging sometimes were grouped with the more standard sloops.
Her commanding officer was usually a commander but sometimes a junior captain. In World War Two, WWII sloops were ocean escorts, with lesser capability than a destroyer or destroyer escort.