 Gilbert and his brothers led the forward policy against Cenel Conaill on behalf of the king but Gilbert was killed at Ballyshannon in 1213.Following the invasion of Connacht by Richard Mór de Burgh in the 1230s Maurice FitzGerald, 2nd Lord of Offaly of the FitzGerald dynasty was granted lands and established the castle, port and town of Sligo.He was to the forefront of pushing the frontier against Tir Conaill and Tir Eoghan until his defeat in the Battle of Creadran Cille at Ros Ceide in 1257.