Sloop-of-war

In the 18th century and most of the 19th, a sloop-of-war in the Royal Navy was a warship with a single gun deck that carried up to eighteen guns. The rating system covered all vessels with 20 guns and above; thus, the term sloop-of-war encompassed all the unrated combat vessels, including the very small gun-brigs and cutters. In technical terms, even the more specialised bomb vessels and fireships were classed as sloops-of-war, and in practice these were employed in the sloop role when not carrying out their specialised functions.

In World War I and World War II, the Royal Navy reused the term "sloop" for specialised convoy-defence vessels, including the Flower class of World War I and the highly successful Black Swan class of World War II, with anti-aircraft and anti-submarine capability. They performed similar duties to the American destroyer escort class ships, and also performed similar duties to the smaller corvettes of the Royal Navy.