Charles William Ferdinand , Duke of Brunswick - Wolfenbüttel Charles William Ferdinand ( German : " Karl Wilhelm Ferdinand , Fürst und Herzog von Braunschweig - Wolfenbüttel " ) ( October 9 , 1735 – November 10 , 1806 ) , Duke of Brunswick - Wolfenbüttel , was a sovereign prince of the Holy Roman Empire , and a professional soldier who served as a Generalfeldmarschall of the Kingdom of Prussia . Born in Wolfenbüttel , Germany , he was duke of Brunswick - Wolfenbüttel from 1780 until his death . He is a recognized master of the modern warfare of the mid - 18th century , a cultured and benevolent despot in the model of Frederick the Great , and was married to Princess Augusta , a sister of George III of Great Britain . The botanical genus " Brunsvigia " was named in his honour . History . Charles William Ferdinand ( ) was the son of Charles I , Duke of Brunswick - Wolfenbüttel and Philippine Charlotte , daughter of King Frederick William I of Prussia . Karl received an unusually wide and thorough education , and travelled in his youth in the Netherlands , France and various parts of Germany . His first military experience was in the North German campaign of 1757 , under Prince William , Duke of Cumberland . At the Battle of Hastenbeck he won great renown by a gallant charge at the head of an infantry brigade ; and upon the capitulation of Kloster Zeven he was easily persuaded by his uncle Ferdinand of Brunswick , who succeeded Cumberland in command , to continue in the war as a general officer . The exploits of the hereditary prince , as he was called , soon gained him further reputation , and he became an acknowledged master of irregular warfare . In pitched battles , and in particular at Minden and Warburg , he proved himself an excellent subordinate . After the close of the Seven Years ' War , the prince visited England with his bride , the daughter of Frederick , Prince of Wales , and in 1766 he went to France , being received both by his allies and his late enemies with every token of respect . In Paris he made the acquaintance of Marmontel ; in Switzerland , whither he continued his tour , that of Voltaire ; and in Rome , where he remained for a long time , he explored the antiquities of the city under the guidance of Winckelmann . After a visit to Naples he returned to Paris , and thence , with his wife , to Brunswick . His services to the dukedom during the next few years were of the greatest value ; with the assistance of the minister Feonçe von Rotenkreuz he rescued the state from the bankruptcy into which the war had brought it . His popularity was unbounded , and when he succeeded his father , Duke Karl I , in 1780 , he soon became known as a model to sovereigns . Reputation . The Duke was a typical " enlightened despot " of the 18th century , characterized by economy and prudence . His habitual caution often made him draw back from potential reforms . He brought Braunschweig into close alliance with the king of Prussia , for whom he had fought in the Seven Years ' War ; he was a Prussian field marshal , and was at pains to make the regiment of which he was colonel a model one , and he was frequently engaged in diplomatic and other state affairs . He resembled his uncle Frederick the Great in many ways , but he lacked the resolution of the king , and in civil as in military affairs was prone to excessive caution . As an enthusiastic adherent of the Germanic and anti - Austrian policy of Prussia he joined the Fürstenbund , in which , as he now had the reputation of being the best soldier of his time , he was the destined commander - in - chief of the federal army . Military experience . First experience . His first military experience was during the Seven Years ' War in the North German campaign of 1757 , under the Duke of Cumberland . He gained great fame at the Battle of Hastenbeck with his gallant charge at the head of an infantry brigade . French Revolutionary Wars . In the early summer of 1792 , Ferdinand was poised with military forces at Coblenz . After the Girondin s had arranged for France to declare war on Austria , voted on April 20 , 1792 , the Catholic Holy Roman Emperor Leopold II and the Protestant King of Prussia Frederick William II had combined armies and put them under Brunswick ' s command . The " Brunswick Proclamation " or " Brunswick Manifesto " that he now issued from Coblenz on July 25 , 1792 threatened war and ruin to soldiers and civilians alike , should the Republicans injure Louis XVI and his family . His avowed aim was : to put an end to the anarchy in the interior of France , to check the attacks upon the throne and the altar , to reestablish the legal power , to restore to the king the security and the liberty of which he is now deprived and to place him in a position to exercise once more the legitimate authority which belongs to him . Additionally , the manifesto threatened the French public with instant punishment should they resist the Imperial and Prussian armies , or the reinstatement of the monarchy . In large part , the manifesto had been written by Louis XVI ' s cousin , Louis Joseph de Bourbon , Prince de Condé , who was the leader of a large corps of émigrés in the allied army . It was asserted the manifesto was in fact issued against the advice of Brunswick himself ; the duke , a model sovereign in his own principality , sympathized with the constitutional side of the French Revolution , while as a soldier he had no confidence in the success of the enterprise . However , having let bear his signature , he had to bear the full responsibly for its consequences . The proclamation was intended to threaten the French public into submission ; it had exactly the opposite effect . In Paris , Louis XVI was generally believed to be in correspondence with the Austrians and Prussians already , and the republicans became more vocal in the early summer of 1792 . It remained for the Duke of Brunswick ' s proclamation to assure the downfall of the monarchy by his proclamation , which was being rapidly distributed in Paris by July 28 apparently by the monarchists , who badly misjudged the effect it would have ( See text in link ) . The " Brunswick Manifesto " seemed to furnish the agitators with a complete justification for the revolt that they were already planning . The first violent action was carried out on August 10 , when the Palace of the Tuileries was stormed . After the French Revolutionary Wars . The Duke of Brunswick had served in the Seven Years ' War and was made a Prussian general in 1773 . After he succeeded to his title in 1780 , he was made field marshal in 1787 , and commanded the Prussian army that rapidly and successfully invaded the United Provinces ( The Dutch Republic ) and restored the authority of the House of Orange . He was less successful against French citizen ' s army that met him at Valmy . Having secured Longwy and Verdun without serious resistance , he turned back after a mere skirmish in Valmy , and evacuated France . When he counterattacked the Revolutionary French who had invaded Germany , in 1793 , he recaptured Mainz after a long siege , but resigned in 1794 in protest at interference by Frederick William II of Prussia . He returned to command the Prussian army in 1806 during the War of the Fourth Coalition but was routed by Napoleon ' s marshal Davout at Battle of Jena - Auerstedt ( 14 October 1806 ) . During the battle he was struck by a musket shot and lost both of his eyes . Mortally wounded the Duke fled before the advancing French Forces and died in Ottensen on November 10 , 1806 . His body was provisionally laid to rest in Christianskirche , before it could be transferred for burial in Brunswick Cathedral on November 6 , 1819 . Children . Karl Wilhelm Ferdinand ' s eldest son and designated heir , Karl Georg August ( 1766 – 1806 ) , married Frederika Luise Wilhelmine , Princess of Orange - Nassau , daughter of William V , Prince of Orange and Wilhelmina of Prussia , in 1790 . He died childless shortly before his father on 20 September 1806 . His successor , Friedrich Wilhelm ( 1771 – June 16 , 1815 ) , who was one of the bitterest opponents of Napoleonic domination in Germany , took part in the war of 1809 at the head of a corps of partisans ; fled to England after the Battle of Wagram , and returned to Braunschweig in 1813 , where he raised fresh troops . He was killed at the Battle of Quatre Bras . The remaining two sons , Georg Wilhelm Christian ( 1769 – 1811 ) and August ( 1770 – 1822 ) , were declared incapacitated and excluded from the line of succession ; neither of them married . The eldest daughter , Auguste Caroline Friederike ( 1764 – 1788 ) , married King Frederick I of Württemberg . The second daughter , Caroline ( 1768 – 1821 ) , married , with very unhappy results , her first cousin King George IV of the United Kingdom .