In 1555, the Holy Roman Emperor Charles V abdicated and King Phillip II of Spain acquired the German and Spanish empires, including the Low Countries. Catholic rebellion in the Netherlands led to the persecution and execution of Protestants under the Duke of Alba and his Council of Troubles (also known as Council of Blood). William of Orange led the Dutch revolt, but his attempts to form a united front against the Spanish failed when the southern states pledged loyalty to King Phillip under the Union of Arras. In response, the northern Protestant provinces formed the Union of Utrecht and allegiance to Prince William of Orange. After the prince’s assassination in 1584, his son Maurice garnered support from the English and over the following years, the Dutch enjoyed a series of victories over the Spanish. The result was the Twelve Years’ Truce, but when this ended in 1621, and the two sides were, once again, enemies in the Eighty Years’ War.