This book is the first detailed volume to cover the famous Norden Bombsight (NBS) which was one of the most secret weapons used before and during World War II by the United States in its bomber aircraft. Development of the NBS was started in 1922 by the Navy Bureau of Ordnance, and in 1932 the famous Mark XV was introduced. Configuration of the NBS, except for changes, remained static through its life, and its accuracy during Allied bombing runs made it one of the most important technical developments of the war. Later several attachments were devised to make it more accurate new optics were developed, ballistic charts updated, and electrical engineering methods refined with the aid of research centers. Electronics were first used in the C-1 auto pilot in 1941, and radar was also used with the NBS, and it was also used in the first guided bombs, called AZON/RAZON, the forerunner of the guided missile. The NBS was again called to duty in 1967-68 in the Vietnam war, before it was phased out of the inventory. This is its complete story.