In 1916 Sean Heuston and a small group of young Irish Volunteers took over the Mendicity Institution on the Dublin Quays. Sean was captain of ‘D’ Company of the Irish Volunteers 1st Battalion but he was also still a senior Fianna officer. Sean held various senior posts in the Fianna organisation at that time; Captain of No. 6 Company, Vice-Commandant of the Dublin Brigade, and also Director of Training at Fianna GHQ.
Several other Irish Volunteers at the Mendicity Institution with Heuston were also members of Fianna Eireann including P. J. Stephenson, Sean McLoughlin, Liam Staines and Dick Balfe.