The fall of Singapore in 1942 showed that Britain could no longer protect its far-flung Dominions. Closer military ties were therefore necessary for New Zealand's defence. With United States entering the war, they were an obvious choice. Links with Australia had also been developed earlier; both nations sent troops to the Anglo-Boer War and New Zealand officer candidates had trained at Australia's Royal Military College, Duntroon since 1911, a practice that continues to this day. A combined Australian and New Zealand Army Corps (ANZAC) was formed for the Gallipoli campaign during World War I, and its exploits are key events in the military history of both countries.