Commandant Michael Mallin and his second in command, Countess Markievicz, were assigned to St Stephen’s Green, a rectangular park, approximately twenty acres in size located a mile south of the General Post Office and close to Jacob’s. The current membership of the Irish Citizen Army was approximately 400; it is estimated that 200-250 turned out during the Rising, most of them serving with Mallin in the St Stephen’s Green area, the main exceptions being those with Seán Connolly at City Hall.

Mallin proceeded to fortify his position, posting men in some of the houses overlooking the Green and setting men to work digging trenches to cover the entrances. He dispatched parties to take over Harcourt Street railway station, J. & T. Davy’s public house at the junction of South Richmond Street and Charlemont Mall, and houses at Leeson Street bridge. It soon transpired that St Stephen’s Green was a vulnerable position, as it was overlooked by the Shelbourne Hotel and some other tall buildings that had not been occupied by Mallin’s forces.

Mallin had military experience, having served for fourteen years in the British army, part of the time as a non- commissioned officer (NCO). Presumably, when St Stephen’s Green was originally selected as a position it was expected that there would be enough men to occupy the Shelbourne Hotel and all the other tall buildings, but that was not the case. The British directed machine gun fire from the Shelbourne onto the Green late on Monday, as a result of which Mallin abandoned most of it on Tuesday.

The majority of the ICA forces then garrisoned the Royal College of Surgeons immediately to the west of the Green. As General Lowe concentrated on the GPO and the Four Courts, the College of Surgeons garrison was involved in little action until the order for surrender came the following Sunday.