Karl was the second son of
Friedrich Anton Ulrich, Prince of Waldeck and Pyrmont and
Countess Palatine Louise of Zweibrücken-Birkenfeld, youngest child of
Christian II, Count Palatine of Zweibrücken-Birkenfeld. In 1728 his father and his elder brother Christian Philip died, and so he became Prince of
Waldeck and Pyrmont. The Waldecks had a tradition of military service in the Dutch Army.
Prince Georg Friedrich of Waldeck had already led the Dutch army in the
War of the Grand Alliance. In the War of Austrian Succession, Karl was appointed as commander of the Dutch Army by the
States-General of the Netherlands, as counterbalance to
William IV, Prince of Orange, who relied completely on his brother-in-law the
Duke of Cumberland. Waldeck was seen as an energetic and capable commander. Unfortunately, the coöperation between the Allied armies was severely lacking. Waldeck was present at the
Battle of Fontenoy, where he led the attacks of the Dutch infantry on the French positions before the Allied commander, the Duke of Cumberland, would launch a massive attack on the French centre. Although having performed rather well at the battle, Waldeck and the infantry commander General baron Cronström were not pleased with the overall state of the troops and launched a series of improvements. He was also present at the
Battle of Rocoux and the
Battle of Lauffeld, all in which the Allies suffered defeat, although the Dutch troops performed much better. In 1746, Karl became Fieldmarshal of the
Holy Roman Empire. In 1747, the French launched an attack on
Bergen op Zoom; Waldeck wanted to come to the relief of the Allied garrison, but was severely hampered by the British and Austrians, who were ordered to spare no troops but rather stay in their positions to protect
Maastricht. Frustrated, Waldeck left the army immediately and returned to his home without officially resigning his command. ==Marriage and children==