The Conscription Crisis of 1917 and Borden's decision to invite the Liberals into a wartime coalition government with the Conservatives split the Liberal Party largely along linguistic lines. Many provincial Liberal parties in English-speaking Canada and a number of Liberal Members of Parliament supported conscription and decided to support Borden's government. Many of them called themselves Liberal Unionists. Quebec Liberals and the leader of the Liberal Party of Canada, Sir Wilfrid Laurier, refused to join Borden, and ran in the resulting election as "Laurier Liberals" or Opposition (Laurier Liberal).
The Conservatives attempted to make their alliance with Liberal Unionists permanent through the formation of the National Liberal and Conservative Party. However, under a new leader, William Lyon Mackenzie King (One of the few English Canadian Laurier Liberals), the Liberals were able to recover enough of their support in English Canada to form a minority government following the 1921 federal election.
See also: List of Canadian political parties