score:11
Southeast New Guinea (Papua) was legally part of Australia during WWII, and there were battles there as the Japanese tried to take out Port Moresby. This includes the advance over the Owen Stanley Mountains and the landing in Milne Bay.
Upvote:4
A Japanese submarine bombarded the suburbs of Sydney, including Rose Bay, with a small cannon. As part of the initial attacks on Northern Australia, there were air raids at several points including a devastating attack on a seaplane base at Broome in North-Western Australia. Eventually the Japanese had to re-deploy the carrier forces that led these attacks (they were largely destroyed at Midway) and the fighting shifted to New Guinea and the Solomons. The Japanese then had few resources to waste in attacks on mainland Australia.
Upvote:5
Aside from attacks during the two already mentioned time periods - European colonisation and the Japanese attacks during WW2 - there was another attack on Australian soil, though not on the continent itself: In the early morning of 2004-09-09, a car bomb was detonated at the Australian embassy in Jakarta, Indonesia.
Of course, an embassy's area isn't, strictly speaking, sovereign territory of the country maintaining it. However, it does enjoy a wide array of protection similar to such a territory and any attack on such can be perceived as an attack on the country itself - and has on occasion been treated as such.
Upvote:10
Depends on what you call "Australia" and "attacks".
One could say that the UK attacked and took over the country from the natives that were there initially.