The Course Setting Bomb Sight (CSBS) is the canonical vector bombsight, the first practical system for properly accounting for the effects of wind when dropping bombs. It is also widely referred to as the Wimperis sight after its inventor, Harry Wimperis. The CSBS was developed for the Royal Naval Air Service (RNAS) in order to attack submarines and ships. It was introduced in 1917, and was such a great advance over earlier designs that it was quickly adopted by the Royal Flying Corps, and the Independent Air Force. It has been called "the most important bomb sight of the war".