With the involvement of Ireland on the outbreak of World War I in August 1914, Devlin sided with Redmond's decision in supporting recruiting[REF] for Britain's and the Allied war effort and voluntary enlistment of National Volunteers in Irish regiments of the New Service Army.
After the 1916 Easter Rising Devlin compromised with Northern Nationalists on a temporary six-county exclusion to assist Lloyd George's abortive home rule negotiations, organising a convention which endorsed exclusion by a vote of 475 to 265 [REF].