The Balao (SS-285) class was conceived as an improved Gato (SS-212) class submarine. Balao introduced several new concepts to the submarine force when she was commissioned in 1943. The most important of these being the thicker pressure hull, using 7/8" high tensile steel plates rather than the 5/8" plate used in the earlier Gato class. Improvements in hull construction increased the test depth of this class to 400-feet as opposed to 350-feet in the Gato class and fuel capacity was significantly increased which improved patrol radius. Submerged endurance was 48 hours at 2 knots. Cruising range was almost 10,000 sea miles on the surface at 10 knots with 116,000 gallons of diesel fuel. Patrol duration was 75 days.