In 1942, to protect Sydney Harbour from a submarine attack, the Sydney Harbour anti-submarine boom net was constructed. It spanned the harbour from Green (Laings) Point, Watsons Bay to the battery at Georges Head, on the other side of the harbour. On the night of 31 May 1942, three Japanese midget submarines entered the harbour, one of which became entangled in the western end of the boom net's central section. Unable to free their submarine, the crew detonated charges, killing themselves in the process. A second midget submarine came to grief in Taylor's Bay, the two crew committing suicide. The third submarine fired two torpedoes at USS "Chicago" (both missed) before leaving the harbour. In November 2006, this submarine was found off Sydney's Northern Beaches.