By the outbreak of the First World War, Britain had little direct authority in North America. The increasing power of the US economy had resulted in a 'triangular' set of relationships between Britain, Canada and the United States. Robert Borden's Conservative Party, which broadly represented English-Canadians in Canada, was in power. The Conservatives supported Britain's war effort with enthusiasm, whatever their economic links with the United States. Over 600,000 Canadians joined the armed forces in the course of the war, playing a key role on the Western Front. However, Borden's attempt to enforce conscription on French-Canadians in 1917 produced opposition in Quebec.
Given the strength of the Canadian contribution to Britain's First World War effort, Borden was able to play a key role in David Lloyd George's Imperial War Cabinet and the Imperial War Conference of 1917. The Conference resolved that a further conference would be held after the war to consider the constitutional status of the colonies. It recommended that the dominions be recognised as 'autonomous nations' within an imperial commonwealth.
The war had grievously damaged Britain's economy and weakened its financial and economic links with the dominions. During the war the London capital markets had been closed to Canada and they turned to the US. Canada's movement towards national autonomy during the 1920s and 1930s, especially under the leadership of the long-serving Liberal Prime Minister, Mackenzie King, further weakened colonial links.
The Chanak crisis of 1922, in which the Canadian government (and other dominions) refused to assist British forces in Turkey, showed that Canada now controlled its foreign policy independently of Britain. In 1923 the Canadian government demonstrated how far this process had gone when it entered into a bilateral treaty with the United States. The Balfour Report of 1926 described the dominions as autonomous and equal states, which were in no way subordinate in any aspect of domestic or foreign affairs. In 1931 the Statute of Westminster confirmed the legislative independence of Canada from Britain.