As such, since 2000 units of the Australian Army Reserve have been deployed to and the on peacekeeping duties and many more individual Reservists have been used to provide specialist capabilities and to fill in Regular Army formations being sent overseas. History [ ] Federation to World War I [ ] Following the Federation of Australia in 1901, the amalgamation of the controlled by the six separate, to form a unified force controlled by the Commonwealth was an inevitable, albeit slowly realised, consequence, given that the new assigned the defence power solely to the Commonwealth. Indeed, this process took some time as, to a large extent, matters of defence were not necessarily a priority of the new Australian legislature at the time, and there was also a considerable diversity in opinion regarding the composition and size of the new national army and role it would play at home and indeed within the wider Imperial defence system. Nevertheless, the official transfer of forces from the states to the Commonwealth occurred on 1 March 1901, and this date is today celebrated as the birthday of the modern Australian Army. At the outset, the bulk of the Commonwealth military force was to be made up of part-time volunteers.