Information:  - The Irish Civil War (28 June 1922  24 May 1923) was a conflict that followed the Irish War of Independence and accompanied the establishment of the Irish Free State, an entity independent from the United Kingdom but within the British Empire.  - The Riddle of the Sands: A Record of Secret Service is a 1903 novel by Erskine Childers. The book, which enjoyed immense popularity in the years before World War I, is an early example of the espionage novel and was extremely influential in the genre of spy fiction. It has been made into feature-length films for both cinema and television.  - The United Kingdom of Great Britain and Ireland was established as a sovereign state on 1 January 1801 by the Acts of Union 1800, which merged the kingdoms of Great Britain and Ireland. The growing desire for an Irish Republic led to the Irish War of Independence, which resulted in Ireland seceding from the Union and forming the Irish Free State in 1922. Northern Ireland remained part of the United Kingdom, and the state was consequently renamed the "United Kingdom of Great Britain and Northern Ireland".  - The Anglo-Irish Treaty, commonly known as The Treaty and officially the Articles of Agreement for a Treaty Between Great Britain and Ireland, was an agreement between the government of the United Kingdom of Great Britain and Ireland and representatives of the Irish Republic that concluded the Irish War of Independence. It provided for the establishment of the Irish Free State within a year as a self-governing dominion within the 'community of nations known as the British Empire', a status 'the same as that of the Dominion of Canada'. It also provided Northern Ireland, which had been created by the Government of Ireland Act 1920, an option to opt out of the Irish Free State, which it exercised.  - Dominions were semi-independent polities under the British Crown, constituting the British Empire, beginning with Canadian Confederation in 1867. They included Canada, Australia, New Zealand, Newfoundland, South Africa, and the Irish Free State, and then from the late 1940s also India, Pakistan, and Ceylon (now Sri Lanka). The Balfour Declaration of 1926 recognised the Dominions as "autonomous Communities within the British Empire", and the 1931 Statute of Westminster granted them full legislative independence.  - Robert Childers Barton ( 4 March 1881 -- 10 August 1975 ) was an Irish nationalist , politician and farmer who participated in the negotiations leading up to the signature of the Anglo - Irish Treaty . His father was Charles William Barton and his mother was Agnes Childers . His wife was Rachel Warren of Boston , daughter of Fiske Warren . His double first cousin and close friend was Robert Erskine Childers .  - The British Empire comprised the dominions, colonies, protectorates, mandates and other territories ruled or administered by the United Kingdom and its predecessor states. It originated with the overseas possessions and trading posts established by England between the late 16th and early 18th centuries. At its height, it was the largest empire in history and, for over a century, was the foremost global power. By 1913, the British Empire held sway over 412 million people, % of the world population at the time, and by 1920, it covered , % of the Earth's total land area. As a result, its political, legal, linguistic and cultural legacy is widespread. At the peak of its power, the phrase "the empire on which the sun never sets" was often used to describe the British Empire, because its expanse around the globe meant that the sun was always shining on at least one of its territories.  - The Irish Free State (; 6 December 192229 December 1937) was an independent state established in 1922 under the Anglo-Irish Treaty of December 1921. That treaty ended the three-year Irish War of Independence between the forces of the self-proclaimed Irish Republic, the Irish Republican Army (IRA), and British Crown forces.  - The Irish War of Independence or Anglo-Irish War or the Tan War was a guerrilla war fought from 1919 to 1921 between the Irish Republican Army (IRA, the army of the Irish Republic) and the British security forces in Ireland. It was an escalation of the Irish revolutionary period into armed conflict.  - Robert Erskine Childers DSC (25 June 1870  24 November 1922), universally known as Erskine Childers, was the author of the influential novel "The Riddle of the Sands" and an Irish nationalist who smuggled guns to Ireland in his sailing yacht "Asgard". He was executed by the authorities of the nascent Irish Free State during the Irish Civil War. He was the son of British Orientalist scholar Robert Caesar Childers; the cousin of Hugh Childers and Robert Barton; and the father of the fourth President of Ireland, Erskine Hamilton Childers.    Given the information above, choose from the list below the object entity that exhibits the relation 'conflict' with the subject 'robert barton'.  Choices: - british empire  - irish civil war  - irish war of independence  - world war i
Answer:
world war i