He promoted the Lutheran faith and played a key role in the political events of his time, including involvement in the Schmalkaldic League and negotiations leading to the Peace of Passau.

[17][note 4] In his early youth, he travelled extensively through the German lands, which included a visit to the court of Elector Frederick III the Wise in Saxony, where he formed importance relations for the future.

[17] Shortly before, on 16 February 1506, the Beilager of William's sisters Elisabeth and Mary, who married the counts John III of Wied [de] and Jobst I of Holstein-Schauenburg-Pinneberg respectively, was celebrated in Dillenburg with the greatest of festivities.

As some of the most important citizens of the state, the hammer smiths of Siegen were granted exemption from feudal duties, and from about 1539, paid 24 raderguilders a year for this instead of the hitherto usual reisigen Pferdes.

[18] When William's baby daughter Magdalene was baptised in November 1522, guests at Siegen Castle [de] included his friend Count Philip II of Hanau-Münzenberg and his young bride Countess Juliane of Stolberg-Wernigerode.

[5][33] On 18 May 1525, William wrote to his brother Henry in the Netherlands, stating that the whole of southern Germany was ablaze with peasant revolt and that he was very worried about it: "Meine Bauern sind gottlob noch ruhig und zufrieden, aber das Wetter ist allenthalben um mich her."

The Hessian Amtmann Balthasar Schrautenbach wrote that the Franconian peasants wanted to expel Landgrave Philip I the Magnanimous of Hesse and put William in his place.

[39] The baptism of their eldest son, William, on 4 May 1533 also took place according to Catholic tradition; a full mass with Latin formulas, with the use of salt, which symbolised the doctrine of faith, and with a real exorcism of the devil.

[12][note 8] During the era marked by religious and political upheavals, including Luther's first published translation of the Bible, the founding of the Society of Jesus by Ignatius of Loyola, and the execution of Thomas More in England, William was involved in numerous mediation assignments.

[37][42] On 10 January 1531, the Schmalkaldic League was founded by the Protestant Elector John of Saxony, Duke Ernest I of Brunswick-Lüneburg, Landgrave Philip I of Hesse, Fürst Wolfgang of Anhalt-Köthen, the counts of Mansfeld and several minor Imperial Estates.

Despite his country being beset by threats of war throughout his reign, he instructed his officials by various mandates to ensure that the land peace renewed by the Emperor on various Imperial Diets was maintained in his county and that all troublemakers, vagrants and beggars were taken into the strictest custody.

Since excessive spending on family celebrations provided particular opportunity for this, William tried to put an end to intemperance at child baptisms, weddings, funerals and guild meetings through strict regulations.

The count's ordinance of 19 December 1555 stipulated "daß über die bestimmte Zeit, wenn abends die Weinglock geläutet ist, kein Wirt länger weder über die Schwell hinaus oder auch sunsten seinen Gästen im Hause Wein reichen oder zapfen soll" ("that after the stipulated time, when in the evening the wine bell is rung, no innkeeper shall serve or tap wine to his guests in the house, nor over the threshold, nor otherwise"), because otherwise "viel Unrats, Mord, Totschlag, Unzucht und alle Untugend gemehret und überhand nimmt, wie neulich ein schrecklich Exempel und Totschlag sich derhalber zugetragen" ("much mischief, murder, manslaughter, fornication and all immorality will increase and prevail, as recently a terrible example and manslaughter took place thereby").

One ordinance of William that characterised him as a profound and far-sighted sovereign was his ban on marriages between relatives: "Dieweil es etzo unter unseren Untertanen gemein wird, dass die Eltern ihr Kind in Verwandt-, Blutfreundschaft und Schwagerschaft im vierten Glied vermählen, daß doch im Rechte verboten" ("Because it is now customary among our subjects for parents to marry off their child in kinship, blood relationship and consanguinity in the fourth degree, which is forbidden by law"), the friends of both parties, when agreeing on a marriage, "sich erstlich der Sippschaft halben gründlich erkundigen, ob und wie nahe die Personen einander verwandt, und so die Verwandtnis zwischen ihnen im dritten oder vierten Glied bestände, alsdann soll dieselbig Ehe ohn unser Wissen und Willen nicht beteidingt, geschlossen noch zugelassen werden" ("first of all thoroughly inquire into the kinship, whether and how closely the persons are related to each other, and if the kinship between them is in the third or fourth degree, this marriage shall not be concluded or allowed without our knowledge and will").

[35] Shortly after the beginning of William's reign, the Augustinian monk Martin Luther initiated the movement of minds, from which the Protestant Church emerged with his Ninety-five Theses in 1517.

These warnings, in view of the already three-decade-long Katzenelnbogische Erbfolgestreit, in which the Emperor was Nassau's most powerful and almost sole supporter, had an effect on William, but neither were they able to dissuade him from his increasingly strong inclination towards Luther's doctrine.

William initiated religious renewal in the county's two main cities, Dillenburg and Siegen, by replacing, in October 1530, the two previous parish priests, who had voluntarily retired in exchange for a mercy salary, with two representatives of the new doctrine.

It was mainly through the mediation of Philipp Melanchthon, who maintained a lively correspondence with William's counsellor Wilhelm Knüttel, that a pupil of the two great reformers from Wittenberg, Erasmus Sarcerius from Annaberg in Saxony, came to the county as a helper.

Substantial resources were expended on numerous legal proceedings, and the rebuilding of Dillenburg Castle into a strong fortress, where soldiers were stationed for years to repel opposition attacks.

[5] The County of Katzenelnbogen was situated between the Taunus and the River Lahn and was very rich due to the possession of a large number of Rhine tolls between Mainz and the border of the Netherlands.

[60] The county consisted of Rheinfels, Sankt Goar, Braubach, Hohenstein, Darmstadt, Zwingenberg, Rüsselsheim and Umstadt, as well as Eppstein, the district of Driedorf and parts of Diez, Hadamar, Ems, Löhnberg, Camberg, Altweilnau [de] and Wehrheim.

Henry's high position and close personal relationship with Charles V as an educator, general and advisor gave the Nassaus a major support in this protracted legal battle.

A commission consisting of the Prince bishops Christoph of Augsburg, George of Bamberg and William III [de] of Strasbourg was given the task of re-examining the case, which had been handled by the most important legal scholars of the time.

[34] The complicated political and religious circumstances of the period, including the wars Charles V had to fight against France and the Turks kept him out of the Holy Roman Empire for a long time.

[33]At that time, construction of the Hohen Mauer (high wall) began under the leadership of Utz or Ulrich von Anspach, who had been Burgrave of Ginsburg Castle [de] since 1516.

In December 1531, the construction of the wall was still being built, when William wrote to his brother that he had only just begun the heavy foundation work for the fortress, which is still entirely unfinished and requires great foresight.

On 24 May 1533, he again described to him his difficult situation: because the landgrave "allenthalben an ihn stoße, könnte er nit wohl sicher aus seinem Haus reiten oder gehn" ("collided with him everywhere, he could not safely ride or go out of his house") and was therefore "zu einem bau und festung höchlich verursacht" ("compelled to a construction and fortification in a high degree").

[65] Philip regarded William as his worst and greatest enemy and adversary, and in 1535 called him a "papistischen Diener" (papist servant), who, like his brother Henry, was "subservient to the House of Burgundy", and wanted to deprive him of the largest and best part of his inherited princely land and people.

[66] After years of fruitless negotiations, an agreement with Hesse was finally reached in Frankfurt on 30 June 1557 through the mediation of Electors Otto Henry of the Palatinate and Augustus of Saxony and the Dukes Christoph of Württemberg and William V of Jülich.

Although it does not hold up to modern-day scrutiny, it did have an impact at the time, mainly due to his appeal to the charisma (royal salvation) that had come to Nassau through Roman King Adolf.