Question: The 1916 Australian plebiscite was held to conscript young Australian men for overseas service at the desire of the head of government whose office exists only through longstanding political convention and what?

Context paragraphs:
Prime Minister of Australia: The Prime Minister of the Commonwealth of Australia is the head of government of Australia.  The individual who holds the office is the most senior Minister of the Crown, the leader of the Cabinet and the chairperson of the National Security Committee.  The Prime Minister also has the responsibility of administering the Department of the Prime Minister and Cabinet.  The office is not mentioned in the Constitution of Australia and exists only through longstanding political convention and tradition.  Despite this, in practice it is the most powerful parliamentary position in Australia.  The individual who holds the office is commissioned by the Governor-General of Australia.

Anzacs (TV series): Anzacs (named for members of the all volunteer ANZAC army formations) was a 1985 5-part Australian television miniseries set in World War I.  The series follows the lives of a group of young Australian men who enlist in the 8th Battalion (Australia) of the First Australian Imperial Force in 1914, fighting first at Gallipoli in 1915, and then on the Western Front for the remainder of the war.

12th Brigade (Australia): The 12th Brigade was an infantry brigade of the Australian Army.  Formed in 1916 as part of the all volunteer First Australian Imperial Force that was raised for overseas service during the First World War, the brigade was part of the 4th Division and fought on the Western Front until the end of the war in November 1918.  During the inter-war years, the brigade was re-formed in Australia as a part-time unit; during the Second World War, the brigade was mobilised for full-time service, but did not serve overseas, undertaking garrison duties in Australia until 1944 when it was disbanded.

Australian Labor Party split of 1916: The Australian Labor Party split of 1916 occurred following severe disagreement within the Australian Labor Party over the issue of proposed World War I conscription in Australia.  Labor Prime Minister of Australia Billy Hughes had, by 1916, become an enthusiastic supporter of conscription as a means to boost Australia's contribution to the war effort.  On 30 August 1916, he announced plans for a referendum on the issue (the Australian plebiscite, 1916), and introduced enabling legislation into parliament on 14 September, which passed only with the support of the opposition.  Six of Hughes' ministers resigned in protest at the move, and the New South Wales state branch of the Labor Party expelled Hughes.  The referendum saw an intense campaign in which Labor figures vehemently advocated on each side of the argument, although the "no" campaign narrowly won on 14 November.  In the wake of the referendum defeat, the caucus moved to expel Hughes on 14 November; instead, he and 23 supporters resigned and formed the National Labor Party.  Frank Tudor was elected leader of the rump party.  Hughes was recommissioned as Prime Minister, heading a minority government supported by the opposition Commonwealth Liberal Party; the two parties then merged as the Nationalist Party of Australia and won the 1917 federal election.  The Nationalist Party served as the main conservative party of Australia until 1931, and the split resulted in many early Labor figures ending their careers on the political right.

Australian Army Nursing Service: The Australian Army Nursing Service (AANS) was an Australian Army Reserve unit which provided a pool of trained civilian nurses who had volunteered for military service during wartime.  The AANS was formed in 1902 by amalgamating the nursing services of the colonial-era militaries, and formed part of the Australian Army Medical Corps.  During World War I, more than 2,286 women joined the AANS AIF for overseas service.  Hundreds more served in the AANS AMF on home service in Australia.  After WWI, the AANS reverted to a Reserve.  The AANS was mobilised again during World War II, and many of its members served overseas.  Following the war several AANS nurses were posted to Japan as part of the British Commonwealth Occupation Force.  The service was renamed the Royal Australian Army Nursing Service (RAANS) in November 1948 and became part of the regular Army the next year.  In 1951 the RAANS achieved corps status, and became the Royal Australian Army Nursing Corps.

44th Battalion (Australia): The 44th Battalion was an infantry unit of the Australian Army.  Originally formed in 1916 for overseas service during World War I, the battalion fought in the trenches along the Western Front in France and Belgium between late 1916 and 1918, before disbanding at the conclusion of hostilities.  During the inter-war years, the 44th became part of the part-time Citizens Force, based in Western Australia.  During World War II, it undertook garrison duties in Australia but was not deployed overseas to fight.  In the post-World War II period the 44th was amalgamated with the 11th Battalion, before being subsumed into the Royal Western Australia Regiment in 1960.

Prime Minister of Canada: The Prime Minister of Canada (French: "Premier ministre du Canada" ) is the primary minister of the Crown, chairman of the Cabinet, and thus head of the Government of Canada, charged with advising the Canadian monarch or federal viceroy on the exercise of the executive powers vested in them by the constitution.  Not outlined in any constitutional document, the office exists only as per long-established convention (originating in Canada's former colonial power, the United Kingdom) that stipulates the monarch's representative, the governor general, must select as prime minister the person most likely to command the confidence of the elected House of Commons; this individual is typically the leader of the political party that holds the largest number of seats in that chamber.  Canadian prime ministers are styled as "The Right Honourable" (French: "Le Très Honorable" ), a privilege maintained for life.

Colin Batch: Colin Batch (born 27 March 1958 in Melbourne, Victoria) is a professional international field hockey coach and former international player from Australia.  Batch is the head coach of the Australian Men's national hockey team the "Kookaburras" following his appointment on Tuesday 6th December 2016.  He was the head coach of the New Zealand Men's national hockey team the "Black Sticks" between 2013-2016.  Prior to this he was the head coach of the Belgium Men's national hockey team the "Red Lions" from 2010–2012.  From 2001–2008 he was the assistant coach of the most successful Australian Men's national hockey team the "Kookaburras" in history.  During this era Australia broke their Olympic hoodoo winning the Gold medal at the 2004 Athens Olympics as well as Bronze at the 2008 Beijing Olympics, Silver at the 2002 and 2006 World Cups, Gold at the 2002 and 2006 Commonwealth Games and Gold at the 2005 and 2008 Champions Trophies.

Australian conscription referendum, 1916: The 1916 Australian plebiscite was held on 28 October 1916.  It was the first non-binding Australian plebiscite, and contained one question concerning military service.  This plebiscite was held due to Prime Minister Billy Hughes' desire to conscript young Australian men for overseas service during World War I.  It was conducted under the "Military Service Referendum Act" 1916.

World War I conscription in Australia: During the second half of World War One, the First Australian Imperial Force experienced a shortage of men as the number of men volunteering to fight overseas declined and the casualty rate increased.  At the time, military service within the Commonwealth of Australia and its territories was compulsory for Australian men, but that requirement did not extend to conflict outside of Australia.  In 1916, Prime Minister Billy Hughes called a plebiscite to determine public support for extending conscription to include military service outside the Commonwealth for the duration of the war.  The referendum, held on 28 October 1916, narrowly rejected the proposal.  A second plebiscite, held a year later on 20 December 1917, also failed (by a slightly larger margin) to gain a majority.

Supporting paragraphs: Australian conscription referendum, 1916 Prime Minister of Australia
Answer: tradition