A huge fort was built at the entrance to Subic Bay. The fort was 350 feet long and 144 feet wide. About the area of a football field. It stood 40 feet out of the water.
To keep ships from trying to enter the bay the fort sported 4 14” guns mounted inside two turrets that could rotate 360 degrees. One turret set higher than the other so it could fire over the top of the second turret. Each gun could launch a projectile 11 miles away. As backup the fort also had 4, 6” guns mounted on each side. These could take out anything trying to come in close under the main guns.
The first week of February 1942 saw the fort come under sustained fire from Japanese 150mm howitzer batteries positioned on the mainland near Ternate. By the middle of March, the Japanese had brought even heavier artillery into range, opening fire with 240mm siege howitzers. They managed to destroy Fort Drum's 3-inch antiaircraft battery, and disabled one of the 6-inch guns. There was some minor damage too one of the armored casemates. Big chunks of the Fort's concrete structure were chipped away by the shelling but the fort was still fully functional and the men inside safe.
The fort finally surrendered and the Japanese used it as their defenses.
Today Fort Drum is a burned out shell. The structure is still in tact since it was built to last.