Swedish statesman. He entered the service of the Swedish state in 1602 and joined the Council of State in 1609. Gustavus II (Adolphus) appointed him Chancellor in 1612, and for the next 22 years the two men worked together. An administrative reformer of note, Oxenstierna also made possible the reconciliation of the Swedish aristocracy to the monarchy. He negotiated the Truce of Altmark with Poland (1629), joined Gustavus in Germany in 1631, and after the king's death in 1632 was responsible for directing Swedish policy throughout the Thirty Years War. He was also the effective ruler of Sweden from 1636 to 1644, when Queen Christina reached her majority. His subsequent relations with her were not always harmonious. On his death, his son Erik succeeded him as Chancellor.