 While Sydney's anti-submarine defences were not yet complete at the time of the attack on Sydney Harbour on the night of 31 May 1942, they were successful in sinking two of the three Japanese midget submarines which attempted to enter the Harbour; one submarine fired two torpedoes at a warship, both of which missed, one hitting another ship.Following the end of the Japanese threat to Australia Sydney's defences were reduced from 1944.The last fortifications were not decommissioned until the 1960s, however.