The dozens of subsequent air raids on Northern Australia in 1942 and 1943 were mainly small and aimed to prevent the Allied air units based there from attacking Japanese positions. The Attack on Sydney Harbour in May 1942 had the goal of diverting Allied forces away from Midway Island prior to the Japanese attempt to capture it and the subsequent Japanese submarine campaigns off the Australian east coast in 1942 and 1943 were attempts to break the supply line between Australia and New Guinea during the New Guinea Campaign. Moreover, the Japanese attempt to capture Port Moresby in New Guinea by advancing along the Kokoda Track and landing at Milne Bay between July and September 1942 aimed to capture the town to complete Japan's defensive perimeter in the region. Once secured, Port Moresby was to have been used as a base from which Japanese aircraft could dominate the Torres Strait and Coral Sea, and not to support an invasion of Australia.