On 14 April 1922 O'Connor was one of a number of IRA leaders in a 200-strong force of that occupied the Four Courts building in the centre of Dublin in defiance of the Provisional Government. They intended to provoke the British troops (who were still in the country) into attacking them, which they thought would restart the war with Britain and re-unite the IRA against their common enemy. They also occupied other smaller buildings regarded as being associated with the former British administration, such as the Ballast Office and the Freemasons' Hall in Molesworth Street, but the Four Courts remained the focus of interest. On 15 June, O'Connor sent out men to collect the rifles that belonged to the mutineers of the Civic Guards.
