On 6 June, "Bang" put to sea on her second war patrol, the timing of which coincided with the preliminaries to the Mariana Islands invasion. Consequently, she was assigned to waters to the west of that island group so that she would be in position to intercept any Japanese warships or transports steaming eastward to parry the American offensive thrust. While en route to her station, the submarine encountered a lone northbound tanker on 14 June. Although hampered by heavy rain squalls and turbulent seas, "Bang" launched a spread of three torpedoes, one of which hit and damaged the target, but did not sink her. The submarine could not finish off this enemy ship because her orders required her to take station as soon as possible.