He came into conflict with King John II Casimir when he found out that his wife, Elżbieta Słuszka was the King's mistress. Radziejowski started to conspire against the King with the enemies, and as a result was sentenced to infamy and banishment (exile) in 1652 by the Sejm Tribunal. He left Poland for Sweden, and convinced the Swedish to attack the Commonwealth. In 1655, Radziejowski accompanied the Swedish forces during their invasion of Poland in the course of The Deluge. He played an important role in persuading the militia (pospolite ruszenie) to surrender at Ujście. In 1662 he was pardoned by the Sejm. In 1667 he went on a diplomatic mission to the Ottoman Empire and died there.