In the fall of 1942, the Army decided to install 90-mm anti-motor torpedo boat (AMTB) batteries in the harbor defenses. Each battery consisted of two fixed and two mobile guns. The mobile guns were kept in storage until an emergency occurred.
The mission of these batteries was to attack enemy motor torpedo boats, to defend against enemy landings, to assist against enemy air attacks and to attack enemy submarines within range.
After considerable discussion, the Office of the Chief of Engineers decided that San Diego would receive three four-gun 90-mm batteries. Battery Cabrillo was located at Point Loma down the hill from the earlier Battery Point Loma with its 4 155-mm guns; Battery Fetterman at Ballast Point; and Battery Cortez on the Silver Strand at Fort Emory. At each battery two guns would be emplaced and two would be mobile.
All three batteries were completed in August 1943 and the six guns were mounted in September. The District Engineer supervised construction of concrete emplacements. The post engineer installed the electricity and the troops performed the necessary labor. The cost of each battery was $20,000.
The guns of Battery Fetterman were first placed on North Island, but were moved to Ballast Point at the request of the U.S. Navy. Fetterman had been rebuilt in 1940 to accommodate an anti-aircraft battery. Nothing remains of the three AMTB batteries today. Battery Fetterman survived until 1986 when it was demolished for a parking lot.
In the following table are the pedigrees of the guns in the three 90-mm AMTB batteries.
- Battery Cabrillo
- Battery Cortez
- Battery Fetterman
- Battery Cortez