In 1692 both brothers fought the French in Flanders and participated in the battles of Steenkerke and Neerwinden. When the war ended in 1697, the Danish King sent them to present-day Ukraine, where they supported the Polish-Saxon troops in the Polish–Ottoman War (1683–1699) against the Turks. In 1700 they fought in the Great Northern War against Sweden, but Denmark was forced to retreat from the war in the same year.