Born at Goch in the Duchy of Cleves, as a child he served as a page for Christoffel van IJsselstein (or Ysselstein), and when he came of age, he joined the banner of William of Orange at the head of twenty–two men at arms, fighting in the Eighty Years' War.

He became unpopular in William's court and after the crushing defeat in the Battle of Gembloux in 1578, he made overtures to the Spanish, who enlisted him as a soldier in the Army of Flanders.

Lewes Lewknor wrote of Schenck's dissatisfaction, 'Nothing ever more moved Skinke than the indignity of this dealing; and so telling the duke, that he would be loath, now he had spent all that ever he had in the Kings service, to be accounted a captain of freebooters, took his leave, bending his mind presently to revenge; and forthwith surprising Nuis by stratagem, delivered both the same, and the castle of Lemmicke, and withal, his own person, into the service of the States; of whom he was received with such honour as to a man of such worthiness belonged.

[6] The next month, he and Adolf van Nieuwenaar were defeated by the Spanish general Juan Baptista de Tassis at the Battle of Amerongen on 23 June 1585.

[7] In March 1586, accompanied by Hermann Friedrich Cloedt, the commander of the fortified town of Neuss, Schenck went to the County of Westphalia at the head of 500 foot and 500 horse.

[8] There, Robert Dudley knighted him by order of Elizabeth, and presented him with a chain valued at a thousand gold pieces.

[12] By 1588, only Rheinberg remained outside the Spanish grasp, and in an effort to salvage the last major garrison in the electorate of Cologne for Gebhard Truchsess von Waldburg, Schenck intercepted and defeated seven companies of foot marching to Friesland, to reinforce Francisco Verdugo.

On the evening of 10 August, he and 20 barges of men made their way down the Waal to Nijmegen, where they planned to enter the city through windows overlooking the river.

The swollen river pushed more than half the barges past their destination; the house they chose to enter was the site of a wedding party, and the alarm was raised.