During 1942 and 1943 Imperial Japanese Navy (IJN) submarines conducted a number of patrols along Australia's east coast. On 16 May 1942 the submarine I-29 attacked the Soviet freighter Wellen south-east of Newcastle, but did not cause any damage to the ship. In response, a naval force was dispatched from Sydney to attempt to locate the submarine and ships were not permitted to sail between Newcastle and Sydney for 24 hours. On 23 May I-29's floatplane flew over Newcastle and Sydney searching for shipping which could be attacked by midget submarines.