In September 1940, during the Battle of Britain, 71 (Eagle) Squadron was formed in Yorkshire as a Royal Air Force squadron manned by American volunteers, and in 1941 it was joined by 121 (Eagle) and 133 (Eagle) squadrons. A total of 244 American and 16 British pilots were posted to these units, which fought against German forces across the English Channel until September 1942, when they were handed over to the United States Army Air Force. During their Royal Air Force service, the three squadrons lost 66 pilots killed in action or while on active service, and they served in valor.