The Society of United Irishmen launched a rebellion in 1798. It began in Leinster and quickly spread to Ulster. The United Irishmen had been founded in 1791 by liberal Protestants in Belfast. Its goal was to unite Catholics and Protestants and make Ireland an independent republic. Although its membership was mainly Catholic, many of its leaders and members in northeast Ulster were Protestant. The Battle of Ballynahinch began on 12 June 1798, when about 4000 United Irishmen camped at Ballynahinch were besieged by the British Army. The British bombarded the town with cannon for a full day until the United Irishmen retreated. Following this, the British burnt sixty-three houses in Ballynahinch and its hinterland. The commander of the United Irishmen, Henry Munro, was betrayed, captured and executed shortly after.