Support for Great Britain during the First World War caused a major political crisis over conscription, with Francophones, mainly from Quebec, rejecting national policies. During the crisis, large numbers of enemy aliens (especially Ukrainians and Germans) were put under government controls. The Liberal party was deeply split, with most of its Anglophone leaders joining the unionist government headed by Prime Minister Robert Borden, the leader of the Conservative party. The Liberals regained their influence after the war under the leadership of William Lyon Mackenzie King, who served as prime minister with three separate terms between 1921 and 1949.