He studied law at the universities of Leuven, Bourges, Heidelberg, and Padua, and traveled in France and Italy before settling permanently in The Hague.

In this capacity his industry, singular grasp of affairs, and persuasive powers of speech speedily gained for him a position of influence.

During the governorship of Leicester, Van Oldenbarnevelt was the leader of the strenuous opposition offered by the States of Holland to the centralizing policy of the governor.

This great office, given to a man of commanding ability and industry, offered unbounded influence in a multi-headed republic without any central executive authority.

Though nominally the servant of the States of Holland, Van Oldenbarnevelt made himself the political personification of the province which bore more than half the entire charge of the union.

In a brief period, he became entrusted with such large and far-reaching authority in all details of administration, that he became the virtual Prime minister of the Dutch republic.

[1] During the two critical years following the withdrawal of Leicester, the Advocate's statesmanship kept the United Provinces from collapsing under their own inherent separatist tendencies.

Also of good fortune for the Netherlands, the attention of Philip II of Spain was at its greatest weakness, instead focused on a contemplated invasion of England.

His task was made easier by receiving whole-hearted support from Maurice of Nassau, who, after 1589, held the office of Stadholderate of five provinces.

The immediate effect of the truce was a strengthening of Van Oldenbarnevelt's influence in the government of the Dutch Republic, now recognized as a free and independent state; external peace, however, was to bring with it internal strife.

It was no secret that this action by the Arminians was taken with the approval and connivance of Van Oldenbarnevelt, who was an upholder of the principle of religious toleration.

He proposed that the States of Holland should, on their own authority, as a sovereign province, raise a local force of 4000 men (waardgelders) to keep the peace.

Van Oldenbarnevelt was, with his friends, kept in strict confinement until November of that year, and then brought for examination before a commission appointed by the States-General, led by Reynier Pauw.

[1] On 20 February 1619, Van Oldenbarnevelt was arraigned before a special court of twenty-four members, only half of whom were Hollanders, and nearly all of whom were personal enemies.

Attempts to obtain a pardon, or at least a commutation of the sentence of death, were made by Maurice's stepmother, Louise de Coligny, and the French ambassador Benjamin Aubery du Maurier, but it was in vain.

On Monday, 13 May 1619, the death sentence was read to Van Oldenbarnevelt; and, therefore, on the same morning, the old statesman, at the age of seventy-one, was beheaded in the Binnenhof, in The Hague.

During Van Oldenbarnevelt's captivity, his servant Jan Francken kept a diary, forty pages long at the time of his execution; a copy was made by a pastor, the Rev Adrian Stolker, in 1825 for wider dissemination, but the original then disappeared until it was rediscovered in 2018 in Van Oldenbarnevelt's home city of Amersfoort.