"Tench"’s first war patrol had begun soon after the invasion of Iwo Jima and continued past the landings on Okinawa. American planners had foreseen the possibility of Japan's attempting to strike back at the Allied forces with what remained of the Imperial surface fleet. They therefore stationed a picket line of submarines off Japan to serve as an early warning system. "Tench" received orders to join this patrol line before concluding her war patrol. She was on station off the western coast of the Japanese home islands when the "Yamato" task force sortied on 6 April to contest the Okinawa landings. "Tench" did not make a sighting, since "Yamato" sortied from the Bungo Suido. That station was assigned , which raised the alarm; the picket line was disbanded, and each submarine turned to its own individual mission. In accordance to orders, "Tench" cleared the area for an air-sea rescue sweep of the East China Sea before ending her patrol. On 8 April, she picked up the pilot and radioman from a dive-bomber from and then headed for Guam where she arrived on 14 April.