[1] Carl Rudolf was the youngest son of Frederick, who had founded the Württemberg-Neuenstadt branch in 1649, and his wife Clara Augusta von Braunschweig.Carl Rudolf entered in Danish service and went to Ireland to support the Protestant William of Orange against the deposed Catholic King James II of England.In the meanwhile, Denmark had reentered the Great Northern War and Carl Rudolf was ordered to take Stralsund from the Swedish, which he accomplished in 1715 after a long siege.Because Frederick August had left no male successors, and the second brother Ferdinand Wilhelm had died in 1701, the Duchy passed to Carl Rudolf.In 1734 he was recalled once more as Generalfeldmarschall of the Holy Roman Empire to defend the Upper Rhine against the French in the War of Polish Succession.