In 1626, he ventured to France to become a soldier of fortune. In 1630, he rose to the rank of a major under Gustavus Adolphus, King of Sweden, during the Thirty Years War.Oxford Dictionary of National Biography, under Robert Barclay. He returned to Scotland in 1636 to serve in the covenanting army, becoming colonel of a cavalry regiment under General John Middleton.Oxford DNB
