In the 18th and most of the 19th centuries, a sloop-of-war in the Royal Navy was a warship with a single gun deck that carried up to eighteen guns. As the rating system covered all vessels with 20 guns and above, this meant that the term sloop-of-war actually 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 actually employed in the sloop role when not carrying out their specialized functions.