Greenling's third war patrol took her off the Japanese home islands. Departing Midway 23 September, the submarine sank the cargo ship Kinkai Maru 3 October, and Setsuyo Maru the next day. She fired three torpedoes at cargo ship Takusei Maru 14 October, scored three hits, and watched her sink in the space of 6 minutes. This attack brought a host of escort vessels to search for Greenling, but she evaded them and attacked a large freighter 18 October. One torpedo set the target aflame, but the second "fish" ran erratically, circled, and almost hit Greenling. The next ran true, however, and cargo ship Hakonesan Maru was sent to the bottom. After destroying a sampan in the Tokyo–Aleutian Islands shipping lanes 21 October, Greenling returned to Pearl Harbor 1 November. The attrition on Japanese shipping by submarines was already being felt and would be a major factor in their eventual defeat.
