<Tr> <Td> Leinster House, home of the Ireland's parliament since 1922 . </Td> </Tr> <Tr> <Td> Parliament Buildings (Stormont). Previously home of Parliament . Now used by the Assembly . </Td> </Tr> <P> Unwilling to negotiate any understanding with Britain short of complete independence, the Irish Republican Army, the army of the newly declared Irish Republic, waged a guerilla war (the Irish War of Independence) from 1919 to 1921 . In the course of the fighting and amid much acrimony, the Fourth Government of Ireland Act 1920 implemented Home Rule while separating the island into what the British government's Act termed "Northern Ireland" and "Southern Ireland". In July 1921 the Irish and British governments agreed to a truce that halted the war . In December 1921 representatives of both governments signed an Anglo - Irish Treaty . The Irish delegation was led by Arthur Griffith and Michael Collins . This abolished the Irish Republic and created the Irish Free State, a self - governing Dominion of the Commonwealth of Nations in the manner of Canada and Australia . Under the Treaty, Northern Ireland could opt out of the Free State and stay within the United Kingdom: it promptly did so . In 1922 both parliaments ratified the Treaty, formalising independence for the 26 - county Irish Free State (which renamed itself Ireland in 1937, and declared itself a republic in 1949); while the 6 - county Northern Ireland, gaining Home Rule for itself, remained part of the United Kingdom . For most of the next 75 years, each territory was strongly aligned to either Catholic or Protestant ideologies, although this was more marked in the six counties of Northern Ireland . </P> <P> The treaty to sever the Union divided the republican movement into anti-Treaty (who wanted to fight on until an Irish Republic was achieved) and pro-Treaty supporters (who accepted the Free State as a first step towards full independence and unity). Between 1922 and 1923 both sides fought the bloody Irish Civil War . The new Irish Free State government defeated the anti-Treaty remnant of the Irish Republican Army, imposing multiple executions . This division among nationalists still colours Irish politics today, specifically between the two leading Irish political parties, Fianna Fáil and Fine Gael . </P>

When did ireland gain its independence from britain