The play of the English factions, however, soon brought the Geraldines into official favour. The struggle between the Houses of York and Lancaster was beginning, and the first effect of it in Ireland was the arrival of Richard, Duke of York as Lord Lieutenant with unlimited powers (1449).

He was the grandson of Roger Mortimer, Earl of March {page 170), and, therefore, descended from Lionel, Duke of Clarence. His policy was to win over the Irish chiefs, and to placate the Irish Normans. He gained the adhesion of both branches of the Geraldines, but although he bestowed offices upon Ormonde, the Butlers remained steadfast adherents of the Lancastrians.

A new element was introduced by English politics into the ancient rivalry. During the Wars of the Roses (1455-85) many of the Anglo-Irish fought on both sides in the numerous battles in England. The Butlers were almost the only supporters of the House of Lancaster in Ireland, and when the Yorkists were for a time defeated, and the Duke of York fled to Ireland (of which he still claimed to be Lord Lieutenant) he was warmly received and supported (1459).