From 1788 until 1870 the defence of the Australian colonies was mostly provided by British Army regular forces . Originally Marines protected the early settlements at Sydney Cove and Norfolk Island , however they were relieved of these duties in 1790 by a British Army unit specifically recruited for colonial service , known as the New South Wales Corps . The New South Wales Corps subsequently was involved in putting down a rebellion of Irish convicts at Castle Hill in 1804 . Soon however shortcomings in the corps convinced the War Office of the need for a more reliable garrison in New South Wales and Van Diemen 's Land . Chief of these shortcomings was the Rum Rebellion , a coup mounted by its officers in 1808 . As a result , in January 1810 the 73rd ( Perthshire ) Regiment of Foot arrived in Australia . By 1870 , 25 British infantry regiments had served in Australia , as had a small number of artillery and engineer units .