On the night of 31 May/1 June 1942, three "Ko-hyoteki" class midget submarines of the Imperial Japanese Navy entered Sydney Harbour with the intention of attacking Allied warships. According to the official account, only one of the submarines, designated "M-24", was able to fire her torpedoes, but both missed their intended target: the heavy cruiser . The torpedoes, fired around 00:30, continued on to Garden Island: one ran aground harmlessly, but the other hit the breakwater against which "Kuttabul" and the Dutch submarine "K-IX" were moored. An alternate conclusion, based in part on contemporaneous log of the diver who found M-24 later on the day of the attack, was that "Kuttabul" had been hit by five-inch shell from the "Chicago" aimed at the K-IX. In either case, the explosion broke "Kuttabul" in two and sank her.