The first years of the new autonomous region were marked by bitter violence, particularly in Belfast. The IRA was determined to oppose the partition of Ireland so the authorities created the (mainly ex-UVF) Ulster Special Constabulary to aid the Royal Irish Constabulary (RIC) and introduced emergency powers to combat the IRA. Many died in political violence between 1920 and 1923, during which Belfast experienced the worst violence in its history. Killings petered out in 1923 after the signing of the Anglo-Irish Treaty in 1922.