Background
He was born in The Hague, where he was baptised at the court-chapel in November 1590.
He was born in The Hague, where he was baptised at the court-chapel in November 1590.
He first served as a captain of an Overijssel company of the Dutch republican army. The influential ambassador Francis van Aarssens was the guardian of the two young brothers. After only a few weeks into their journey they were invited to the court of King Henry IV of France.
Reinier did not stay long in Paris, and soon returned to the Netherlands in order to marry.
Willem enjoyed himself in Paris so much with the game Jeu de Paume, that van Aerssen sent worried letters to the Netherlands, writing that Willem was neglecting his mathematics study there. Johan van Oldenbarnevelt was not pleased with this, and he let it be known that he would like to see Willem being given a post at the French court.
On August 7, 1608, Willem was appointed a gentleman-ordinary of King Henry IV, which gave him a salary of 3000 Dutch guilders, a post that was probably given for political reasons. Nonetheless, William remained a passionate fan of Jeu de Paume, and wasted his entire salary at the tennis court.
On May 7, 1611 he was knighted by King James I of England, and a few days later, on May 30, he was made Captain at Bergen op Zoom.
In 1616 Willem van Oldenbarnevelt married Walburch van Marnix van Sint-Aldegonde, granddaughter of Philip van Marnix van Sint-Aldegonde. He was appointed governor of Bergen op Zoom in 1617 thanks to mediation by his father. After the execution of his father on May 13, 1619, he was removed from his functions, and was left destitute by the seizure of the possessions of his father, Johan van Oldenbarnevelt.
They hired a number of sailors for 400 guilders to carry out the attack.
The assassination was to take place on February 7, 1623, but the plan leaked out one day early. Reinier van Oldenbarnevelt was arrested and beheaded in The Hague.
Willem managed to escape to Brussels, which was controlled by the Spaniards. Later, letters sent by him to Hugo de Groot were found, which he wrote in the period from January 23, 1626 to 9 December, 1633.
His testament, however, showed that he had become Catholic and had entered service in the Spanish army.