After completing trials and shakedown out of New London, Connecticut, "Tench" departed that port on 20 December for duty in the Pacific. Following brief pauses for training at Key West, Florida, and in the Panama Canal Zone, she reached Pearl Harbor during the latter part of January 1945. An additional training period followed her arrival in Oahu, but only a brief one. On 7 February, she stood out of Pearl Harbor, bound for her first war patrol. After a stop at Saipan for fuel, "Tench" returned to sea in a four submarine wolf pack with , (like "Tench", also the lead ship of a submarine class), and .