When the United States was suddenly thrust into the Second World War in December of 1941, the Navy soon realized the need for long-range land-based bombers to support offensive and defensive operations throughout the vast expanses of the Pacific.

This need was based on the fact that land-based aircraft were superior to seaplanes in anti-shipping and anti-submarine roles due to their greater speed, heavier bomb-load, and amount of defensive armament.  These land-based bombers could also be used to support future offensive actions and to further isolate bypassed Japanese forces.

As a result of the need to procure long-range land-based aircraft, the Navy requested Consolidated B-24 Liberators from the U.S. Army Air Force (USAAF).  Due to their own need for long-range heavy bombers, the USAAF was initially reluctant to provide the Navy with them, however, an agreement was finally reached on July 7, 1942. This agreement called for the transfer a specified number of USAAF Consolidated B-24 Liberators, North American B-25 Mitchells, and Lockheed B-34 Venturas to the Navy.  In return, the Navy agreed to cancel production of its newest seaplane, the Boeing PBB-1 Sea Ranger. As the PBB-1 was being built at Boeing's Renton, Washington production facility, the cancellation of this program would permit Boeing to produce and deliver the B-29 Superfortress to the USAAF on a much earlier schedule.

In February 1943 when the first B-25s became available for transfer to the Navy, the Navy no longer required them. The Navy had already began to receive the B-24s (designated PB4Y-1) and B-34s (designated PV-1) and they had no need for the B-25s. The Marine Corps however, was looking for a bomber that had a greater range than the single-engine types they were currently using. Having been accustomed to receiving obsolete or surplus equipment from the Navy and Army, the Marine Corps gladly accepted these B-25s to fill this need.

In Navy and Marine Corps service the B-25 was designated as the PBJ-1, using the Navy's standard system of identifying its aircraft: "PB" referring to the aircraft's type—Patrol Bomber; "J" referring to the aircraft's manufacturer—North American Aviation, and; "-1" denoting that it was the first patrol bomber manufactured by North American Aviation to be accepted for Naval service.  Suffixes of "C" "D" "G" "H" or "J" were added following the "-1" to denote the specific model type.  These suffixes corresponded exactly to the USAAF's B-25 model designations:  B-25C as the PBJ-1C; B-25D as the PBJ-1D; B-25G as the PBJ-1G; B-25H as the PBJ-1H, and; B-25J as the PBJ-1J.

The Navy accepted 706 PBJ-1s of various models between November 20, 1943 and June 11, 1945 as indicated below. 

By canceling production of the PBB-1 Sea Ranger (top), the Navy was able to acquire land-based B-24, B-34 and B-25 bombers from the USAAF.  These became the PB4Y-1, the PV-1, and the PBJ-1.