The Northern Ireland conflict has its roots in the failure of the British state-building project to consolidate the territorial gains of colonization in Ireland. A decade of intense political activity in the early 20th century, a failed armed rebellion in 1916 and a guerrilla war by the Irish Republican Army (IRA) in 1918–21 led to the establishment of an independent Irish state. The British Government, after a bitter but ultimately failed attempt at counter-insurgency, withdrew its forces from most of Ireland, but the price to be paid was partition. The particular circumstances of the settler plantations from the 17th century onwards had led to well-organized opposition in the north-east to Irish independence, and these supporters of union with Britain were termed ‘unionists’. They had a sufficiently strong alliance with elements of the British political establishment to persuade the British Government to adopt a policy of partition, even after they had failed to defeat the wider challenge of Irish nationalism.