first. In this arrangement, the boat's four main diesel engines drove only electric generators, which supplied power to high-speed electric motors geared to the propeller shafts. The engines themselves were not connected to the propeller shafts. For submerged propulsion, massive storage batteries supplied electricity to the motors. Problems arose with flashover and arcing in the main electric motors. There was also a loss of in transmission through the electrical system. The Winton Model 16-201A 16-cylinder diesels also proved problematic, and were eventually replaced with 12-278As. Five of the class received an additional pair of external bow torpedo tubes, probably early in World War II: Porpoise, Pike, Tarpon, Pickerel, and Permit. The original Mark 6 3 inch (76 mm)/50 caliber deck gun was eventually replaced during the war by the Mark 21 model. The new gun provided a nominal anti-aircraft capability because it allowed high elevations, although this capability was rarely used in combat. Plunger received a Mark 9 4 inch (102 mm)/50 caliber gun during an overhaul in 1943. The boats also originally carried two water jacketed M2 Browning .50 caliber machine guns, with one mounted on the "cigarette deck" on the aft end of the conning tower fairwater and one on a mount on the main deck forward. These guns were taken below when the boat submerged. These boats were all built with a large bulky conning tower fairwater with an enclosed (but free-flooding) wheelhouse and a surface steering station at the forward end. Two periscopes were fitted, one that let into the control room and one that let into the conning tower. The original 30 foot periscopes proved to be too short and were later replaced with 34 foot models. Boats in class The Porpoise class consisted of the P-1 Type, P-3 Type, and P-5 Type subclasses: Service Following participation in exercises from 1937, all but three of the ten Porpoise class were forward deployed to the Philippines in late 1939. In October 1941 most of the front-line submarine force, including all sixteen Salmon and Sargo class boats, joined them. The Japanese occupation of southern Indo-China and the August 1941 American-British-Dutch retaliatory oil embargo had raised international tensions, and an increased military presence in the Philippines was felt necessary. The Japanese did not bomb the Philippines until 10 December 1941, so almost all of the submarines were able to get underway prior to the attack. War experience showed