Captain Seán Heuston of Commandant Daly’s 1st Battalion was deployed to occupy the Mendicity Institution as an outpost about a half-mile to the west of the Four Courts on the south side of the Liffey. His function was to control the route between the nearby Royal Barracks (later Collins Barracks, now the National Museum of Ireland) and the Four Courts for a few hours so that Daly and the remainder of the 1st Battalion would have time to settle in. Immediately on taking over the premises (a home for the down-and-out), Heuston expelled the inmates and fortified the building. Soon after, a force from the Royal Barracks attacked the building, but was repulsed.

Initially Heuston’s force consisted of thirteen Volunteers, but it was reinforced on Tuesday by another thirteen Volunteers from Swords under Captain Richard Coleman. Although required to hold the position for only a matter of hours, the force held out until noon on Wednesday. By then, the Mendicity Institution was surrounded by vastly superior forces equipped with small arms, grenades and heavy machine guns. To save the lives of his remaining men, Heuston surrendered.