James was the Commanding Officer of the 3rd Battalion Decies Brigade of the I.R.A. during the War of Independence and the Civil War. He escaped to Canada after the ceasefire.
A detailed account of the Irish War of Independence from a local point of view including information about James, and one of his brothers, Michael, can be found on the Museum website www.waterfordmuseum.ie which includes the following incident: For several months previous to January 1920, Captain King, who was the Police Inspector in Dungarvan, had been making a nuisance of himself. He drove out to the Mansfield home and threatened to shoot Hannah Mansfield unless she informed on her sons. A group of Dungarvan Volunteers took the Captain's car which was in a garage over half a mile from his house. They then pushed it through the town to his front door where they drenched it with petrol and set it on fire. Shortly afterwards the Captain was transferred to Mallow at his own request. This little operation was carried out by Pax Whelan, Joe Wyse, George Lennon, Pat Lynch and Pat Power. The fact that a group of Volunteers could destroy a policeman's car by fire in broad daylight in the centre of Dungarvan shows the power of the West Waterford Brigade at that time.