By this stage the British began to grow alarmed and suspicious at the growth in support for Sinn Fein and the Volunteers. In May 1918 under the alleged reason of a German Plot, de Valera and other prominent Sinn Fein leaders were arrested. He was jailed in England from May 1918 to 3 February 1919, where he escaped from Lincoln prison. The very first session of the Dail was held in January 1919, but de Valera was absent from this meeting. Nonetheless he was present when the Dail met for the second time in 1 April 1919. He was duly elected as Priomh Aire, the position that was temporarily held by Cathal Brugha at the first session of the Dail. .
From the offset he immediately declared his stance towards those who opposed his position and the position of those who were democratically elected by the people of Ireland i.e. The British Crown. He declared from Dail Eireann, at a public sitting on 10 April 1919 that "that there is in Ireland at this moment only one lawful authority and that authority is the elected government of the Irish Republic." Immediately he set about making life as difficult as possible for the British administration in Ireland. Even though, in comparison to the force that he had at his disposal in comparison to that of the British, de Valera proclaimed that "we shall conduct ourselves towards them in such a way as will make it clear to the world that we acknowledge no right of theirs." .
De Valera was very anxious to point out what the Irish/Gaelic term "Sinn Fein" actually meant. Many, mainly those who saw reason to oppose de Valera assumed that "Sinn Fein" meant "Ourselves Alone", bringing them to the conclusion that he and Sinn Fein wanted an isolation policy for Ireland, that Ireland wanted to stay free from all international and global politics. De Valera was very quick to point out however that "Sinn Fein" did in fact mean "We Ourselves" and all that the Irish people wanted was to be able to govern, rule and conduct their own affairs concerning all Irish domestic and foreign policies.