In October 1915 the Australian Prime Minister, Andrew Fisher of the Australian Labor Party, retired; Billy Hughes was chosen unanimously by the Labor caucus to succeed him. Hughes was a strong supporter of Australia's participation in World War I, and after a visit to Britain in 1916, where the Military Service Act 1916 had been passed earlier in the year, he became convinced that conscription was necessary if Australia was to sustain its contribution to the war effort. A majority of his party, most notably Roman Catholics and trade union representatives, was opposed to this, especially given the British government's reprisals against the Irish Easter Rising of 1916.