scouted Nouméa, Suva, then Auckland, while I-29 went to Sydney. On 11 May, I-22, I-24, I-27, and I-28 were ordered to proceed to the Japanese naval base at Truk Lagoon, in the Caroline Islands, to each receive a Ko-hyoteki-class midget submarine. I-28 failed to reach Truk; she was torpedoed on the surface by the US submarine on 17 May. The three remaining submarines left Truk around 20 May for a point south of the Solomon Islands. I-24 was forced to return a day later when an explosion in her midget submarine's battery compartment killed the midget's navigator and injured the commander. The midget submarine intended for I-28 replaced the damaged midget. Allies The naval officer-in-charge of Sydney Harbour at the time of the attack was Rear Admiral Gerard Muirhead-Gould of the Royal Navy. On the night of the attack, three major vessels were present in Sydney Harbour; the heavy cruisers and , and the light cruiser . Other warships in the harbour included: destroyer tender , auxiliary minelayer , corvettes , , and , armed merchant cruisers and , and Dutch submarine K-IX. A converted ferry—HMAS Kuttabul—was alongside at Garden Island where she served as a temporary barracks for sailors transferring between ships. The hospital ship Oranje had also been in the harbour, but departed an hour before the attack. Harbour defences At the time of the attack, the static Sydney Harbour defences consisted of eight anti-submarine indicator loops—six outside the harbour, one between North Head and South Head, and one between South Head and Middle Head, as well as the partially constructed Sydney Harbour anti-submarine boom net between George's Head on Middle Head and Laing Point (formerly known as Green Point) on Inner South Head. The central section of the net was complete and support piles were in place to the west, but wide gaps remained on either side. Material shortages prevented the completion of the boom net prior to the attack. On the day of the attack, the six outer indicator loops were inactive; two were not functioning and there were not enough trained personnel to man both the inner and outer loop monitoring stations. The North Head – South Head indicator loop had been giving faulty signals since early 1940, and as civilian traffic regularly passed over the loop, readings were often ignored. Harbour defence craft included the anti-submarine vessels and Bingera; the auxiliary minesweepers HMAS Goonambee