In 1942 five batteries of AMTB guns protected the San Pedro Harbor. There were four batteries of 90-mm guns and 37-mm guns and one of only 37-mm guns. These were fast-firing weapons, which were supplemented with 50-caliber machine guns and searchlights as needed. The 90-mm batteries were four guns, two of which were permanent and two mobile. These were supplemented with two mobile 37-mm guns.
These batteries were located at the Gaffey Bulge where Gaffey Street winds around Battery Leary-Merriam; JAAN No. 1, Navy Field; JAAN No. 2, Bluff Park; and Terminal Island.
The fifth battery was designated Dolphins. This was a line of 10 37-mm guns on towers with searchlights located along the harbor breakwater - making a total of 34 guns.
AMTB JAAN No 2 was armed with two M1903 3-Inch Seacoast Guns.