The UDR was raised in 1970, soon after the beginning of the Northern Ireland "Troubles". Before then, the main security forces were the Royal Ulster Constabulary (RUC) and the Ulster Special Constabulary (USC), the most notorious unit of which was the "B Specials". Despite one-third of its positions being reserved for Catholics, Catholics were reluctant to join what they saw as unionist militias that lacked impartiality leading to the forces becoming almost entirely Protestant.