III of Prussia, neutral at the time, promoted a Franco-Prussian convention of 23 May 1802, in addition to the Treaty of Amiens, that gave the House of Orange a few abbatial domains in Germany, that were combined to the Principality of Nassau-Orange-Fulda by way of indemnification for its losses in the Batavian Republic. The stadtholder gave this principality immediately to his son. When Napoleon invaded Germany in 1806 and war broke out between the French Empire and Prussia, William supported his Prussian relatives, though he was nominally a French vassal. He received command of a Prussian division which took part in the Battle of Jena–Auerstedt. The Prussians lost that battle and William was forced to surrender his troops rather ignominiously at Erfurt the day after the battle. He was made a prisoner of war, but was paroled soon. Napoleon punished him for his betrayal, however, by taking away his principality. As a parolee, William was not allowed to take part in the hostilities anymore. After the Peace of Tilsit William received a pension from France in compensation. In the same year, 1806, his father, the Prince of Orange died, and William not only inherited the title, but also his father's claims on the inheritance embodied in the Nassau lands. This would become important a few years later, when developments in Germany coincided to make William the Fürst (Prince) of a diverse assembly of Nassau lands that had belonged to other branches of the House of Nassau. But before this came about, in 1809 tensions between Austria and France became intense. William did not hesitate to join the Austrian army as a Feldmarschalleutnant (major-general) in May 1809 As a member of the staff of the Austrian supreme commander, Archduke Charles he took part in the Battle of Wagram, where he was wounded in the leg. Tsar Alexander I of Russia played a central role in the restoration of the Netherlands. Prince William VI (as he was now known), who had been living in exile in Prussia, met with Alexander I in March 1813. Alexander promised to support William and help restore an independent Netherlands with William as king. Russian troops in the Netherlands participated with their Prussian allies in restoring the dynasty. Dynastic considerations of marriage between the royal houses of Great Britain and the Netherlands, assured British approval. Return After Napoleon's defeat at Leipzig (October 1813), the French troops retreated