The Battle of Attu began when U.S forces landed on Attu on 11 May 1943, and "I-35" got underway for the Attu area. On 13 May 1943, the destroyer , screening the battleship off Attu, detected a stationary submarine on sonar. As "Phelps" was about to attack, the submarine suddenly changed speed and bearing, apparently attempting evasive maneuvers. "Phelps" dropped two depth charges, then lost contact. She regained contact at 15:30 and dropped five and four depth charges. Nearby, the light minelayer signaled confirmation that "Phelps" had hit the submarine and reported that a metal drum and a small diesel oil slick had come to the surface. The identity of the submarine "Phelps" attacked is unknown, but it probably was either "I-34" or "I-35", both of which were in the area at the time. A depth charge presumably had knocked the metal drum off the submarine's deck, but no Japanese submarine was sunk in the action.