The Nationalist Party, also known as the National Party, was an Australian political party. It was formed in February 1917 from a merger between the Liberal Party and the National Labor Party, the latter formed by Prime Minister Billy Hughes and his supporters after the 1916 Labor Party split over World War I conscription. The Nationalist Party was established as a 'united' non-Labor opposition that had remained a political trend once the Labor party established itself in federal politics. The party was in government (from 1923 in coalition with the Country Party) until electoral defeat in 1929. From that time it was the main opposition to the Labor Party until it merged with pro-Joseph Lyons Labor defectors to form the United Australia Party (UAP) in 1931. The party is a direct ancestor of the Liberal Party of Australia, the main centre-right party in Australia. 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. In October Hughes held a plebiscite to try to gain approval for conscription, but the proposition was narrowly defeated. Daniel Mannix, the Catholic Archbishop of Melbourne, was his main opponent on the conscription issue. The defeat did not deter Hughes, who continued to vigorously argue in favour of conscription. This produced a deep and bitter split within the Australian public, as well as within his own party.