forces (See Irish War of Independence). The campaign created tensions between the political and military sides of the nationalist movement. The IRA, nominally subject to the Dáil, in practice, often acted on its own initiative. At the top, the IRA leadership, of Michael Collins and Richard Mulcahy, operated with little reference to Cathal Brugha, the Dáil's Minister for Defence or Éamon de Valera, the President of the Irish Republic – at best giving them a supervisory role. At local level, IRA commanders such as Dan Breen, Sean Moylan, Tom Barry, Sean MacEoin, Liam Lynch and others avoided contact with the IRA command, let alone the Dáil itself. This meant that the violence of the War of Independence rapidly escalated beyond what many in Sinn Féin and Dáil were happy with. Arthur Griffith, for example, favoured passive resistance over the use of force, but he could do little to affect the cycle of violence between IRA guerrillas and Crown forces that emerged over 1919–1920. The military conflict produced only a handful of killings in 1919, but steadily escalated from the summer of 1920 onwards with the introduction of the paramilitary police forces, the Black and Tans and Auxiliary Division into Ireland. From November 1920 to July 1921, over 1000 people died in the conflict (compared to c. 400 until then). Present day Northern Ireland is not a part of the Republic, but it has a nationalist minority who would prefer to be part of a united Ireland. In Northern Ireland, the term "nationalist" is used to refer either to the Catholic population in general or the supporters of the moderate Social Democratic and Labour Party. "Nationalism" in this restricted meaning refers to a political tradition that favours an independent, united Ireland achieved by non-violent means. The more militant strand of nationalism, as espoused by Sinn Féin, is generally described as "republican" and was regarded as somewhat distinct, although the modern-day party claims to be a constitutional party committed to exclusively peaceful and democratic means. 55.8% of voters in Northern Ireland voted for the United Kingdom to remain a part of the European Union in the 23 June 2016 referendum in which the country as a whole voted to leave the union. The results in Northern Ireland were influenced by fears of a strong border between Northern Ireland and the Republic of Ireland as well as by fears of a hard border