The Protestant Unionist party effectively controlled the political system in Ulster After Irish Independence (1922). The large Catholic minority were excluded by ‘gerrymandering’ of electoral constituencies and suffered discrimination in employment and housing. The police force, the Royal Ulster Constabulary, was heavily Protestant. The Bogside Riots (1969) by Catholics against ‘Orange’ marchers, marked a descent into violence, which dramatically escalated after 14 died in the British army’s suppression of rioters on Bloody Sunday (1972). Sinn Fein, the left-wing republican party with the goal of integration with Ireland, practised a two-fold ‘Ballot-box and Armalite’ strategy; its official wing pursued political means, the Provisionals unleashed insurgency and terrorism, particularly bombings. The British government responded with its army and internment of suspected terrorists; the Protestants formed their own terrorist paramilitaries, the Ulster Defence Association. After the bombing campaign increasingly spread to the British mainland, in the 1990s peace negotiations saw the entry of Sinn Fein into government through power-sharing.