Dutch statesman and lawyer who played a key role in the Dutch Revolts. A Calvinist and a keen supporter of William I (the Silent), he helped to negotiate the Union of Utrecht (1579). After 1586, as leader of the Estates of Holland, he managed to impose unity on the diverse political, economic, and religious interests of the United Provinces. He negotiated a twelve-year truce with Spain in 1609, but after this his political differences with Maurice of Nassau became part of a bitter internecine quarrel between two rival schools of Calvinism, and eventually Maurice had Oldenbarneveldt tried and executed on a charge of treason.