When William Rufus died, Arnulf de Montgomery joined his elder brother, Robert of Bellême, in rebellion against Henry I, William's brother and successor as king; when the rebellion failed, he was forced to forfeit all his British lands and titles. Henry appointed his castellan, but when the chosen ally turned out to be incompetent, the King reappointed Gerald in 1102. By 1138 King Stephen had given Pembroke Castle to Gilbert de Clare who used it as an important base in the Norman invasion of Ireland.