Having broken the Japanese codes, American naval intelligence men were able to anticipate Japanese movements. One intercepted enemy message told of an important convoy steaming toward "Tirante's" area. In response to this information, the submarine laid an ambush on 9 April. Picking out two targets, she fired three torpedoes at each. One spread missed, but the other struck the 5,500-ton transport Nikko Maru— carrying homeward-bound Japanese soldiers and sailors from Shanghai. As the important auxiliary slipped beneath the waves, enemy escorts leapt to the offensive. To ward off the counterattack, "Tirante" fired a "cutie" (a small anti-escort homing torpedo) at one of the escorts and heard subsequent "breaking-up noises." But again, post-war accounting failed to confirm the sinking.