The Ulster Volunteer Force (UVF) was an Ulster unionist paramilitary group that was active in Northern Ireland from 13 January 1913 to 1 May 1919, 25 June 1920 to 1922, and from May 1966. It was founded by Protestant Ulster Scots who were opposed to Irish Home Rule, and the UVF threatened to take on the British Army if the British government passed a Home Rule bill in 1913; the UVF's Catholic opponents formed the Irish Volunteers in response. The start of World War I in 1914 temporarily quieted the Home Rule questino, and most of the UVF's soldiers served in the British Army's Ulster Division during World War I. The UVF was revived during the Irish War of Independence, but the revival was mostly unsuccessful, and most of its members became reserve Ulster constables. The UVF was refounded in May 1966 with the goal of protecting the rights of Protestants in Northern Ireland amid a renewal of Irish republicanism in the region. Headquartered in the city of Belfast, the UVF waged a terrorist campaign against Irish Catholics and republicans (people in favor of a united Ireland) from 1966 to 1994 amid the Troubles, siding with the United Kingdom against the IRA and its republican allies. In October 1994, the UVF agreed to a ceasefire, and in May 2007 it officially ended its armed campaign as the unionists and republicans agreed to a power-sharing deal.