During the civil war, he remained neutral and tried to organise a truce to end the fighting. In December 1922, he formed a group called the "Neutral IRA", along with Sean O'Hegarty, composed of pro-truce IRA men. O'Donoghue claimed he had 20,000 members in this group. He campaigned for a month's truce between the two sides, so that a political compromise could be reached. However, his efforts came to nothing and in March 1923, he wound up the "Neutral IRA", judging that its objectives could not be achieved. The civil war ended in late April 1923.