Units operating these specially equipped aircraft were designated Defense Systems Evaluation Squadrons (DSES). The 4713th Defense Systems Evaluation Squadron was stationed for training in the Northeast. The 4713th also deployed frequently to USAFE in West Germany for training of NATO forces. The other was the 4677th Defense Systems Evaluation Squadron, which concentrated on Fighter Interceptor Squadron training for units in the Western United States. In 1974, the 4713th DSES was inactivated and its EB-57s were divided between two Air National Guard units and the 4677th DSES was redesignated as the 17th Defense Systems Evaluation Squadron. This unit was inactivated in July 1979 and was the last to fly B-57s in the active duty USAF. It shared the Defense Systems Evaluation mission with the Kansas and Vermont Air National Guard. Defense Systems Evaluation operations were also carried out by the 6091st Reconnaissance Squadron, Yokota AB, Japan; later the 556th Reconnaissance Squadron and moved to Kadena AB, Okinawa. EB-57s were also deployed to Alaskan Air Command, Elmendorf AFB, Alaska, frequently.