The Northrop P-61 Black Widow was the first aircraft type assigned to the newly formed Air Defense Command.

On March 21, 1946, the Army Air Forces had undertaken a major reorganization to incorporate many of the lessons learned from World War II, a major component of this reorganization included the establishment of three new combat commands in the United States.  Strategic Air Command (SAC), to provide a long-range striking force capable of bombardment operations in any part of the world, the Tactical Air Command (TAC), to support the operations of ground forces, and Air Defense Command (ADC), to provide for the air defense of the United States. 

Air Defense Command headquartered at Mitchell Field, New York, on 27 March 1946 assumed control of the 414th Night Fighter Squadron, which was an un-manned and un-equipped administrative organization, and the 425th Night Fighter Squadron, which was manned by one officer and two enlisted men. Two bases, Mitchell Field, New York and Hamilton Field, California, were assigned to ADC. Two numbered air forces, the First Air Force (Mitchell) and Fourth Air Force (Hamilton) were also established.  

As the Army Air Force organized units, they would reactivated some of its most historical organizations, one of those, the 325th, standing up as the 325th Fighter Group (All Weather) on 21 May 1947 at Mitchell Field, NY. On the same day the 318th was the first squadron reactivated under the Group (with no men or equipment) also located at Mitchell.  On 02 Dec 1947, the unit moved to Hamilton Field, CA with the 325th Fighter Group. At Hamilton, the 318th began to receive personnel and aircraft, the Northrop P-61 Black Widow.

Beginning in early 1946, an Army Air Force team of 15 pilots held secretive trials at McChord Field testing the performance of P-61's ability to intercept invading bombers. The appearance of the Soviet Tupolev Tu-4 'Bull' (copy of the B-29 Superfortress) in 1947 posed a new threat to postwar USAAF planners.

Before beginning a long association with McChord Field/AFB After reactivation without personnel or equipment at Mitchel Field, NY the 318th Fighter Squadron (All Weather) received its first aircraft, the Northrop P-61 Black Widow at Hamilton Field, CA in 1948

During a number of simulated raids on the United States carried out by Strategic Air Command, defending F-51 Mustangs and F-47 Thunderbolts, being used as interceptors, repeatedly failed to find the incoming bombers, or when they knew they were on their way, rarely got themselves into a firing position. If the fighters intercepted the bombers, it was usually too late since the bombers (primarily B-29 Superfortresses) would have already completed their bomb runs over the intended targets of New York City, Los Angeles, Seattle, Chicago and St. Louis.

It was found that the radar-equipped P-61's were very effective in locating and attacking the incoming SAC bombers, and had the range to attack the bombers far from their intended targets. In the late 1940s, there was not a jet US interceptor ready to perform the interceptor mission, so the ADC used the Black Widow as an interim measure.

In September of 1946, the Air Defense Commands Fourth Air Force formally activated the 425th Night Fighter Squadron at McChord flying the P-61s, the Commands first squadron to be activated with personnel and equipment. On 25 August 1947, the 425th NFS was redesignated as the 317th Fighter Squadron, the next year, the 318th rejoin its former group mate at McChord with their North American F-82 Twin Mustangs on 26 November 1948, rejoining the 325th All Weather Fighter Group Headquartered at Moses Lake AFB, WA.

In September of 1946, the Air Defense Commands Fourth Air Force formally activated the 425th Night Fighter Squadron at McChord flying the P-61s, the Commands first squadron to be activated with personnel and equipment. On 25 August 1947, the 425th NFS was redesignated as the 317th Fighter Squadron, the next year, the 318th rejoin its former group mate at McChord on 26 November 1948, rejoining the 325th All Weather Fighter Group Headquartered at Moses Lake AFB, WA.