O'Brien, alarmed at the increased activity of Sinn Féin in 1915, predicted the danger of a potential republican eruption, culminating in the IRB 1916 Rebellion, in which however Sinn Féin were not involved. He was forced to cease publication of his "Cork Free Press" in 1916 soon after the appointment of Lord Decies as Chief Press Censor for Ireland. Decies warned the press to be careful about what they published. Such warnings had little effect when dealing with such papers as the "Cork Free Press". It was suppressed after its republican editor, Frank Gallagher, accused the British authorities of lying about the conditions and situation of republican prisoners in the Frongoch internment camp.