The Laginian invasion made little impact in Ulster or Munster, where Ernean tribes continued to be the dominant force. But the same cannot be said for Connacht, the westernmost of the four provinces. Sometime in the third century (all these dates are highly conjectural) they crossed the River Shannon and subjugated the Ernean tribes of Connacht. The decisive battle, the "Cath Maige Tuired", was fought in County Sligo in a place called Mag Tuired. There a Laginian king (possibly known as Cairbre) overthrew the Érainn and drove them out of Connacht. According to Irish records the defeated Érainn sought refuge in many of the islands around Ireland. The fortresses of Dún Aonghasa and Dún Conor on the Aran Islands, and Dún Balor on Tory Island, are thought to have been built by them.