The Royal Ulster Constabulary (RUC) was the police force of Northern Ireland from 1 June 1922 to 4 November 2001, replacing the Royal Irish Constabulary and preceding the Police Service of Northern Ireland. The RUC had 8,500 officers and 4,500 reservists at its height during The Troubles, and it was used to combat the IRA and other Irish republicans. 319 RUC constables were killed and 9,000 injured in paramilitary assassinations or attacks, while the RUC killed 55 people (including 28 civilians) during the period. The RUC was known for one-sided policy and discrimination, often siding with the Protestant Ulster Scots unionists against the oppressed Catholic Irish population. However, it was praised as one of the most professional policing operations by the United Kingdom, the mother government of Northern Ireland, and it remained the trusted police force in the region until the PSNI replaced it in 2001.