William the Silent : biography
Later, in his Apology (1580), William stated that his resolve to oppose the King’s policies had originated in June 1559, when, during a hunting trip to the Bois de Vincennes together with the duke of Alva and King Henry II of France, to whom both had been sent as hostages to ensure the proper fulfilment of the conditions of the Treaty of Cateau-Cambrésis following the Hispano-French war, the latter two had openly discussed a secret understanding between Philip and Henry which aimed at the extermination of the Protestants in both France and the Netherlands; William at that time had kept silent, but had decided for himself that he would not allow the slaughter of so many innocent subjects.
In early 1565, a large group of lesser noblemen, including William’s younger brother Louis, formed the Confederacy of Noblemen. On 5 April, they offered a petition to Margaret of Parma, requesting an end to the persecution of Protestants. From August to October 1566, a wave of iconoclasm (known as the Beeldenstorm) spread through the Low Countries. Calvinists, Anabaptists and Mennonites, angry with their being persecuted by the Roman Catholic Church and opposed to the Catholic images of saints (which in their eyes conflicted with the Second Commandment), destroyed statues in hundreds of churches and monasteries throughout the Netherlands.
Following the Beeldenstorm, unrest in the Netherlands grew, and Margaret agreed to grant the wishes of the Confederacy, provided the noblemen would help to restore order. She also allowed more important noblemen, including William of Orange, to assist the Confederacy. In late 1566, and early 1567, it became clear that she would not be allowed to fulfil her promises, and when several minor rebellions failed, many Calvinists (the major Protestant denomination) and Lutherans fled the country. Following the announcement that Philip II, unhappy with the situation in the Netherlands, would dispatch his loyal general Fernando Álvarez de Toledo, Duke of Alba (also known as "The Iron Duke"), to restore order, William laid down his functions and retreated to his native Nassau in April 1567. He had been (financially) involved with several of the rebellions.
After his arrival in August 1567, Alba established the Council of Troubles (known to the people as the Council of Blood) to judge those involved in the rebellion and the iconoclasm. William was one of the 10,000 to be summoned before the Council, but he failed to appear. He was subsequently declared an outlaw, and his properties were confiscated. As one of the most prominent and popular politicians of the Netherlands, William of Orange emerged as the leader of an armed resistance. He financed the Watergeuzen, refugee Protestants who formed bands of corsairs and raided the coastal cities of the Netherlands (often killing Spanish and Dutch alike). He also raised an army, consisting mostly of German mercenaries to fight Alba on land. William allied with the French Huguenots, following the end of the second Religious War in France when they had troops to spare.Wedgwood (1944) p. 104. Led by his brother Louis, the army invaded the northern Netherlands in 1568. However the plan failed almost from the start. The Huguenots were defeated by French Royal Troops before they could invade, and a small force under Jean de Villers was captured within two days. Villers gave all the plans of the campaign to the Spanish following his capture.Wedgwood (1944) p. 105. On 23 May, the army under the command of Louis won the Battle of Heiligerlee in the northern province of Groningen against a Spanish army led by the stadtholder of the northern provinces, Jean de Ligne, Duke of Aremberg. Aremberg was killed in the battle, as was William’s brother Adolf. Alba countered by killing a number of convicted noblemen (including the Counts of Egmont and Hoorn on 6 June), and then by leading an expedition to Groningen. There, he annihilated Louis’ forces on German territory in the Battle of Jemmingen on 21 July, although Louis managed to escape.Wedgwood (1944) p. 108. These two battles are now considered to be the start of the Eighty Years’ War.