On the extinction of the native dynasty of the O'Connors, the town fell into the hands of the De Burgos, the head of a branch of which, under the name of M`William Eighter, long governed it by magistrates of his own appointment.
However, the effects of Brian's revolution were permanent; the prescriptive rights of the Hy Neill were disputed, and from the battle of Clontarf until the coming of the Normans the history of Ireland consisted of a struggle for ascendancy between the O'Brians of Munster, the O'Neills of Ulster and the O'Connors of Connaught.
On the other hand, the De Burghs, partly by alliance with the Irish, partly by sheer hard fighting, made good their claims to the lordship of Connaught, and the western O'Connors henceforth play a very subordinate part in Irish history.
The family quarrels of the O'Connors at this time, and their alliances with the Burkes, or De Burghs, and the Berminghams, may be traced in great detail in the annalists - the general result being fatal to the royal tribe of Connaught, which is said to have lost ro,000 warriors in the battle of Templetogher.
The O'Mores and O'Connors were brought low, and forts erected where Maryborough and Philipstown now stand.
The plan of settling Leix and Offaly by dividing the country between colonists and natives holding by English tenure failed, owing to the unconquerable love of the people for their own customs. But resistance gradually grew fainter, and we hear little of the O'Connors after this.