William, Count of Nassau-Siegen (13 August 1592 – 17 July 1642), German: Wilhelm Graf von Nassau-Siegen, official titles: Graf zu Nassau, Katzenelnbogen, Vianden und Diez, Herr zu Beilstein, was Count of Nassau-Siegen, a part of the County of Nassau from 1624 to 1642. A member of the House of Nassau-Siegen, a cadet branch of the Ottonian Line of the House of Nassau, he was a professional soldier who served in the armies of the Hanseatic League and the Republic of Venice, then with the Dutch States Army during the Eighty Years War. Promoted field marshal in 1633, he was successively governor of Emmerich, Heusden and Sluis.
William was born in Dillenburg on 13 August 1592, the fifth son of Count John VII 'the Middle' of Nassau-Siegen and his first wife, Countess Magdalene of Waldeck-Wildungen. He studied in Heidelberg and then went – along with the later 'Winter King' Frederick of the Palatinate – to the court of Henri de La Tour d'Auvergne, the Duke of Bouillon, in Sedan. With Landgrave Otto of Hesse-Kassel William visited England.
William began his military career in 1610 in his father's army in the Upper Palatinate. In 1615 he was captain in the Army of the Hanseatic League to end the siege of Brunswick. In 1617 he joined his eldest brother John Ernest, who was a general for the Republic of Venice in the Uskok War.
After the end of the Twelve Years' Truce in 1621, William recruited troops for the Dutch Republic in the County of Nassau and entered the Dutch States Army in that same year. He was appointed colonel of the infantry on 24 July 1622, but lived in Siegen until 1625. In 1625 he became governor of Emmerich, then of Heusden from 1626 to 1637. The States of Holland refused on 25 November 1626 to make an exception for William to the rule that no military charges could be accumulated, and the Gecommitteerde Raden of Holland decided on 12 December 1626 not to oppose a proposed increase in William's salary in the States General but to allow it to fade away. At the baptism of his daughter Hollandine in March 1628, the States of Holland were prepared to sponsor, complete with a baptismal gift (which meant they were willing to spend money on an annuity for life).
During the Siege of 's-Hertogenbosch in 1629, William had his headquarters in Orthen, from where 's-Hertogenbosch was first shelled on 15 May. Accompanied by 24 companies of infantry and some cavalry, William was sent to the Bommelerwaard by Prince Frederick Henry of Orange to prevent an invasion by Hendrik Graaf van den Bergh, then commander of the Army of Flanders. In the year 1629, William's salary was £400, equivalent to £89,594 in 2025, per month.
In the winter of 1629–1630, William was sent with his troops east of the Rhine to Cleves, Mark, Jülich and Berg, but without providing sufficient funds. In January 1630, Hendrik van der Capellen, gecommiteerde ter velde (representative of the States General of the Dutch Republic at the Dutch State Army), complained in a letter to Prince Frederick Henry that if the Dutch garrisons of Duisburg and Essen did not receive one month's pay immediately, sy het alsoo ergh als de Keisersche maken sullen (transl. they will make it as bad as the Imperial troops) and cause the citizens to leave those cities. The prince argued in response that it were vrembde maximen (transl. strange maxims) to worry about this, because after all die Landen den Vurst van Nieuburch toebehoorende waeren, ende dat het Volck alleene gesonden was om desen winter aldaer geïnquartiert te worden (transl. the lands belonged to the Prince of Neuburg, and the troops had only been sent to be quartered there this winter). In Soest Walraven van Gendt also complained but the presence of these soldiers forced the Spanish troops to withdraw from Unna, Hamm and Lippstadt, leaving them to the Dutch. In fact, William's troops returned in 1630 after some unrest over their overdue pay, albeit in a rather desolate state.
In 1631 William purchased the heerlijkheid of Poederoijen on the River Meuse. During the March along the Meuse in 1632, William and his troops initially kept an eye on the situation near the front in Zeeland until he was summoned by Prince Frederick Henry of Orange to the Siege of Maastricht in late July. William captured the Kruisschans on the Scheldt and Fort Sint-Anna and other sconces near Antwerp, later Orsoy, in the following year the Sterreschans and those of Philippine in State Flanders. In 1632 William was appointed ritmeester of the cuirassiers and in April 1633 succeeded his uncle Count Ernest Casimir of Nassau-Diez as Field marshal.
In 1636, the strongly defended Schenkenschanz was captured from the Spanish by William and his brother John Maurice. In 1637, William became governor of Sluis and took part in the Siege of Breda; being paid £7000, equivalent to £1,304,740 in 2025, for his service. In support of his planned attack on Antwerp, in 1638 Prince Frederick Henry entrusted William with an important undertaking, the occupation of the levee at Calloo. Having taken the sconces of Stabroek and Calloo and chased off their Spanish defenders, William stopped and awaited reinforcements instead of continuing his march. Receiving false intelligence that a larger Spanish force was approaching, he hastily retreated but was caught and defeated at the Battle of Kallo on 17 June. He lost over 2,000 men, including his son Maurice Frederick, which meant Frederick Henry's entire enterprise failed. During the Siege of Gennep in 1641, William received a musket shot in the abdomen, from which he later succumbed.
Settlement of the succession by Count John VII 'the Middle'
Because the county of Nassau-Siegen was so small (it had about 9,000 inhabitants and yielded an annual revenue of about 13,000 guilders) William's father John VII 'the Middle' decided that the county should not be divided again. He made a will and testament in 1607, which stated that only the eldest son would rule and the other children should be compensated with money or offices. As one of the most convinced advocates of Protestantism, it was particularly painful for John that his second son, John 'the Younger', converted to the Catholic Church in 1613. In a codicil of 8 October 1613 he explicitly stipulated that his heirs had to keep the land in the Reformed confession. At first, the conversion of John 'the Younger' did not change this house law established by the will, because John Ernest was the eldest son.
To the surprise of his relatives, John 'the Younger' joined the Spaniards in 1617, the opponents of the House of Nassau and the Dutch Republic. In the same year, his older brother John Ernest died in the service of the Republic of Venice. John 'the Middle' had to decide whether an enemy of Nassau and the Netherlands could remain his heir. On 15 November 1617, John declared his will of 8 April 1607 to be null and void. Abolition of the primogeniture would have meant a division of the small country and John opposed all proposals in that direction. In an amicable agreement, he had his son sign a declaration on 31 December 1617, in which the latter declared that, although he remained a Catholic, he would not force his subjects to any other than the existing religious confession. On 22 December 1618 John drew up a second will, which promulgated the promises of his son as a condition and still held on to the primogeniture. He imposed the penalty of disinheritance on the introduction of 'papism'.
Why John 'the Middle' still distrusted his son, in spite of the latter's confirmations, cannot be fully elucidated. Maybe it was because John 'the Younger' loudly proclaimed that no power in the world could prevent him from succeeding in Nassau-Siegen, because the power of the Emperor and the King of Spain was behind him. Perhaps John 'the Middle' also knew the influence of the de Ligne family and the Catholic clergy on his son. It is certain that such rumours were conveyed to him from all sides and that his relatives and other Protestant estates of the realm warned him again and again about his son. Only when John 'the Middle' was convinced that his son was under the influence of the Jesuits and that the possibility of a Catholic area within the Nassau lands was a danger to the Protestant inhabitants, was he persuaded to make a new will. On 3 July 1621 John 'the Middle' drew up a third will, in which he laid down that the small county of Nassau-Siegen, which was barely able to support one lord, was to be split into three parts. His three eldest sons, John 'the Younger', William and John Maurice, were to receive one third each. The administration of the city of Siegen would remain in joint ownership.