A dominion was a wholly self-governing territory of the former British Empire: Canada received practical independence, at least in internal affairs, upon the confederation of its constituent provinces in 1867, Australia on the federation of its colonies in 1901, New Zealand in 1907, the newly-created Union of South Africa in 1910 and the Irish Free State (later Eire) in 1922. All retained the British monarch as head of state, to be represented locally by a Governor-General appointed in consultation with the Dominion government. Newfoundland was accorded Dominion status by the Statute of Westminster in December 1931, but self-government was suspended two years later and the territory became a province of Canada in 1949.
The foreign relations of the Dominions were initially conducted through the Foreign Office of the United Kingdom: Canada created a Department of External Affairs in June 1909, but diplomatic relations with other governments continued to be channelled through the Governors-General, Dominion High Commissioners in London (first appointed by Canada in 1880; Australia followed only in 1910) and British legations abroad, although a Canadian War Mission in Washington, D.C. dealt with supply matters from February 1918 to March 1921. Britain's declaration of war against Germany in August 1914 was deemed to extend without the need for consultation to all territories of the Empire, occasioning some displeasure in Canadian official circles and contributing to a brief anti-British insurrection by Afrikaner militants in South Africa later that year.
Although the Dominions had had no formal voice in declaring war, each was included separately among the signatories of the June 1919 peace Treaty of Versailles, which had been negotiated by a British-led united Empire delegation. In September 1922 Dominion reluctance to support British military action against Turkey influenced Britain's decison to seek a compromise settlement. Diplomatic autonomy soon followed, with the U.S.-Canadian Halibut Fisheries Agreement (March 1923) marking the first international treaty negotiated and concluded entirely independently by a former colony. The Dominions section created within the Colonial Office in 1907 was upgraded in June 1925 to a separate Dominions Office, though it shared a common Secretary of State with the Colonial Office until June 1930.
The principle of Dominion equality with Britain and independence in foreign relations was formally ratified by the Balfour Declaration adopted at the Imperial Conference of November 1926 and enshrined in the Statute of Westminster, adopted by the British Parliament in December 1931 and subsequently ratified by the Dominion Parliaments. In 1928 Canada obtained the appointment of a British High Commissioner in Ottawa, separating the administrative and diplomatic functions of the Governor-General, ending the latter's anomalous role as the representative of the British Government in relations between the two countries. Canada's first permanent diplomatic mission to a foreign country opened in Washington in 1927 (gaining Embassy status in 1943): Australia followed in 1940.
Britain's declaration of hostilities against Germany in September 1939 did not commit the Dominions, leaving them to issue their own declarations of war except for neutral Eire, which had negotiated the removal of British forces from its territory the year before. The political ties between Britain and the Dominions were further loosened by World War II, which fatally undermined Britain's already weakened commercial and financial leadership and heightened the importance of the United States as a source of military assistance. Australian prime minister John Curtin's unprecedented action (February 1942) in successfully demanding the recall for home service of Australian troops earmarked for the defence of British-held Burma demonstrated that Dominion governments could no longer be expected to subordinate their own national interests to British strategic perspectives.
The Dominions Office merged with the India Office as the Commonwealth Relations Office upon the independence of India and Pakistan in August 1947, and the term "Dominion" fell out of use as India's adoption of republican status in November 1949 signalled the end of the former dependencies' common constitutional connection to the British crown (although Ireland had already dropped its oath of allegiance to the King in 1937): henceforth all members of what was subsequently styled The Commonwealth agreed to accept the British monarch as head of that association of independent states. Eire had formally ceased to be a member seven months earlier upon becoming the Republic of Ireland.