Adolf van Nieuwenaar Adolf van Nieuwenaar , Count of Limburg and Moers ( also : Adolf von Neuenahr ) ( c . 1545 – 18 October 1589 ) was a statesman and soldier , who was stadtholder of Overijssel , Guelders and Utrecht for the States - General of the Netherlands during the Eighty Years ' War . Early life . Nieuwenaar ( as he is usually called in historiography ) was the son of Count Gumprecht II von Neuenahr - Alpen and Amöna von Daun . After the death of his father in 1556 he was raised at the court of his guardian and uncle , the Protestant Count Hermann of Neuenahr and Moers , who was married to Magdalene , a half - sister of William the Silent , Prince of Orange . In 1570 he married his aunt Anna Walburga von Neuenahr , the widow of Philip de Montmorency , Count of Hoorn who had been executed by the Duke of Alba in 1568 . She was the sister of his guardian Hermann . When Count Hermann died childless in December 1578 , Niewenaar inherited his lands , including the county of Moers . All these lands are close to the current border between Germany and the Netherlands , and abutted the Duchy of Guelders in the Habsburg Netherlands . Participation in the Cologne War . Nieuwenaar encouraged the Prince - elector and Archbishop of Cologne Gebhard Truchsess von Waldburg to retain his control of the Electorate of Cologne after he married Agnes von Mansfeld - Eisleben and converted to Calvinism . In 1583 Pope Gregory XIII excommunicated Gebhard , and the Cathedral chapter chose Ernest of Bavaria as the new Elector . War broke out between the two rivals : it was known as the Cologne War . Gebhart was supported by Nieuwenaar ( as his general ) , his brother , Karl , Truchsess von Waldburg - Trauchburg and the Dutch rebels . Ernest by his brothers , Wilhelm V , Duke of Bavaria , Ferdinand of Bavaria , and eventually by Spain . By 1586 , Nieuwenaar was driven out of all his German possessions . Stadtholderate . However , he soon found a new position in the rebellious Netherlands . The stadtholder of the province of Gelderland in the States - General , Willem IV van den Bergh , had been caught in treasonous correspondence with the Spanish Governor - General of the Habsburg Netherlands , Alexander Farnese , Duke of Parma , and had been deposed in November 1583 . Nieuwenaar was now appointed the new stadtholder . As such he only controlled the city of Arnhem and surroundings , however . Most of the province was in Spanish hands . In August 1584 , Nieuwenaar ' s uncle , the Prince of Orange , who at the time was also Stadtholder of Utrecht and Overijssel , was assassinated . After some delay , the States - General appointed Nieuwenaar as stadtholder of these provinces in his uncle ' s place . In Utrecht a political struggle ensued between radical Calvinists and more conservative nobles and regents . In this conflict , Robert Dudley , 1st Earl of Leicester , who became the new Governor - General on the side of the States - General in the northern Netherlands in 1585 , chose the side of the radicals , and so did Nieuwenaar . However , after Leicester ' s departure for England in 1587 , Nieuwenaar gradually changed his stance . He brought about a ( nominal ) reconciliation between the warring parties . After a bloodless coup in 1588 the radicals were ousted from the city of Utrecht , but this did not undermine Nieuwenaar ' s position as stadtholder . As stadtholder , Nieuwenaar was also commander - in - chief of the military forces of the States - General in his provinces . As such he led several campaigns , but with little success . He captured Neuss in 1585 , but this city was soon lost again to Spain . During his retreat , Nieuwenaar destroyed Kamp Abbey in 1586 . In 1585 , the Spanish general Juan Baptista de Tassis defeated him and Maarten Schenk van Nydeggen at the Battle of Amerongen on 23 June 1585 . Schenk would in the same year build the fortress of Schenkenschans ( Schenk ' s fortress ) on his orders . Nieuwenaar died in an explosion at Arnhem , while testing a new piece of artillery , on 18 October 1589 .