Most of the Low Countries had come under the rule of the House of Burgundy and subsequently the House of Habsburg. In 1549 Holy Roman Emperor Charles V issued the Pragmatic Sanction, which further unified the Seventeen Provinces under his rule. Charles was succeeded by his son, King Philip II of Spain. In 1568 the Netherlands, led by William I of Orange, revolted against Philip II because of high taxes, persecution of Protestants by the government, and Philip's efforts to modernize and centralize the devolved-medieval government structures of the provinces. This was the start of the Eighty Years' War.