Sinn Féin MPs elected in 1918 fulfilled their election promise not to take their seats in Westminster but instead set up an independent "Assembly of Ireland", or "Dáil Éireann", in the Irish language. In theory, the Volunteers were responsible to the Dáil and was the army of the Irish Republic. In practice, the Dáil had great difficulty controlling their actions; under their own constitution, the Volunteers were bound to obey their own executive and no other body. The fear was increased when, on the very day the new national parliament was meeting, 21 January 1919, members of the Third Tipperary Brigade led by Séumas Robinson, Seán Treacy, Dan Breen and Seán Hogan carried out the Soloheadbeg Ambush and seized a quantity of gelignite, killing two RIC constables and triggering the War of Independence. Technically, the men involved were considered to be in a serious breach of Volunteer discipline and were liable to be court-martialed, but it was considered more politically expedient to hold them up as examples of a rejuvenated militarism. The conflict soon escalated into guerrilla warfare by what were then known as the "Flying Columns" in remote areas. Attacks on remote RIC barracks continued throughout 1919 and 1920, forcing the police to consolidate defensively in the larger towns, effectively placing large areas of the countryside in the hands of the Republicans.