When recalcitrant barons rebelled against John late in 1215, Hubert scored several important military victories for the royal cause. By 1217, a year after the accession of the nine-year-old Henry III, the insurrection was suppressed. Burgh became the dominant figure in the government upon the death of the regent, William Marshal, Earl of Pembroke, in 1219, and in 1228 he was created justiciar for life. Nevertheless, Henry had already (1227) declared himself a monarch of full age; it was only a matter of time before he would throw off Hubert's tutelage. In 1229 Henry unjustly blamed him for the failure of an expedition against France, and in 1231 the justiciar's bitterest enemy, Peter des Roches, returned from a crusade and won the king's favour. Henry then dismissed Hubert (July 1232) and imprisoned him on charges of treason. In 1234 he was pardoned and reconciled with the king.