The histories of Australia and New Zealand have run along parallel, though not identical, trajectories. In 1901, when the Australian federation was formed from six self-governing colonies, New Zealand was asked to join. It did not, but the Commonwealth of Australia Constitution Act 19002 left open the possibility that it might one day change its mind. Though this has never happened, the bilateral relationship since 1901 has been almost familial, with the two peoples linked by language, open immigration and cultural affinity (even if Australians cannot resist playing the gratuitously insensitive big brother). Most particularly, the nations are linked by a shared memory of World War I. In this conflict the two peoples often fought together, including in the Australian and New Zealand Army Corps, from which the acronym ANZAC was derived. They also embraced a common valorising narrative arising from the war, the Anzac legend or myth. Although 'Anzac' (to use the common shorthand), has played a more dominant role in the Australian political culture than in New Zealand, to this day the rituals of Anzac Day, the anniversary of the landing at Gallipoli on 25 April 1915, are commemorated jointly, in each country and at overseas sites of war memory. There is, therefore, much in the two peoples' experience of World War I that is common. But there were also differences, particularly on the issue of conscription for service in the war.