The Stronghold of Charlemont proved to be of great strategic importance in the Irish Confederate Wars in the 1640s, as it was one of only a handful of modern fortresses to be found in Ireland at that time. It was captured by the forces of Felim O'Neill in 1641 and the Ulster army of the Irish Confederates managed to hold onto the fort throughout the 1640s. It was eventually captured by Charles Coote after he had been reinforced by New Model Army soldiers in late 1650, but hundreds of Cootes soldiers were killed in the effort.