Son of Charles William Ferdinand. During the Napoleonic Wars, from 1806 to 1813, France occupied Brunswick-Wolfenbüttel. Died in battle at Quatre Bras. Frederick William's son Charles (a minor at the time of his father's death) became the first Duke of independent Brunswick. Duchy of Brunswick
Regencies of William, Duke of Austria and Leopold IV, Duke of Austria (1404-1411) Succeeded as a minor, under guardianship of his Leopoldinian uncles. He was elected, in 1437–38, as King of Bohemia and King of Hungary , and also as King of Germany , beginning a three centuries long succession of Habsburg rulers as Kings of the Romans and Holy Roman Emperors .