Attack On Sydney Harbour - Harbour Defences

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 Green Point on Inner South Head. The central section of the net was complete and support piles were in place to the west, but 400 m (1,300 ft) 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 HMAS Yandra and Bingera; the auxiliary minesweepers HMAS Goonambee and Samuel Benbow; pleasure launches converted to channel patrol boats (and armed with depth charges), namely HMAS Yarroma, Lolita, Steady Hour, Sea Mist, Marlean, and Toomaree; and four unarmed auxiliary patrol boats.