Three Marine-manned antiaircraft positions were located outside the Cavite Navy Yard: Battery A, across the bay at Canacao Golf Course on the tip of Sangley Point; Battery B at Carridad; and Battery C at Binacayan one mile south. Each held four 3-inch, .50-caliber, dual-purpose guns with a range of about 15,000 feet. Battery D was divided to support each position with five .50-caliber machine guns.
On 10 December, two Japanese combat teams came ashore in northern Luzon, securing airfields for their Army aircraft to support more landings. However, there was no alarm in Cavite. As usual, civilian workers came into the Navy Yard and quickly went to work. The only sign of war was a detachment of Filipino workers digging an air-raid trench in the yard of the Commandancia, Admiral Rockwell's headquarters. The half-completed trench was the only air-raid shelter in the Navy Yard. Only the antiaircraft weapons had been revetted. Four 3-inch antiaircraft guns were mounted at the ammunition depot in the yard, as well as numerous .50-caliber machine guns mounted around the yard.
