Through fortunes of marriage and inheritance, Warwick emerged in the 1450s at the centre of English politics. Originally, he was a supporter of King Henry VI; however, a territorial dispute with Edmund Beaufort, Duke of Somerset, led him to collaborate with Richard, Duke of York, in opposing the king. From this conflict, he gained the strategically valuable post of Captain of Calais, a position that benefited him greatly in the years to come. The political conflict later turned into full-scale rebellion, where in battle York was slain, as was Warwick's father Salisbury. York's son, however, later triumphed with Warwick's assistance, and was crowned King Edward IV. Edward initially ruled with Warwick's support, but the two later fell out over foreign policy and the king's choice to marry Elizabeth Woodville. After a failed plot to crown Edward's brother, George, Duke of Clarence, Warwick instead restored Henry VI to the throne. The triumph was short-lived, however: on 14 April 1471, Warwick was defeated by Edward at the Battle of Barnet, and killed.