 During his early years as Archbishop, at the time of the Irish Civil War, he tried to bring about peace by calling a conference of the leaders, but no basis for agreement could be found.Arguing that the majority of the Irish people supported the Treaty, he advised de Valera not to split the Sinn Féin party, even if he was defeated in the Dáil; however, this advice was ignored.Byrne objected to the execution of Erskine Childers and other anti-Treaty supporters, and the policy of reprisals by both parties.