Bernard received an unusually good education and studied briefly at the University of Jena, but soon went to the court of Duke John Casimir of Saxe-Coburg to engage in knightly exercises. At the outbreak of the Thirty Years' War he took the field on the Protestant side, and served under Mansfeld at Wiesloch (1622), under the Margrave of Baden at Wimpfen (1622), and with his brother William at Stadtlohn (1623). Undismayed by these defeats, he took part in the campaigns of King Christian IV of Denmark. After a severe defeat in Holstein in 1627, Bernhard left danish service and went to the Dutch Republic. There he was present at the famous Siege of 's-Hertogenbosch in 1629.