Prince Frederick Henry Louis of Prussia (; 18 January 1726 – 3 August 1802) was a Prussian general, statesman, and diplomat. He was a son of King Frederick William I of Prussia and Princess Sophia Dorothea of Hanover, and the younger brother of Frederick the Great. Prince Henry led Prussian armies in the Silesian Wars and the Seven Years' War, having never lost a battle in the latter. In 1786, he was suggested as a candidate to be a monarch in the United States.
Biography
Born in Berlin, Henry was the 13th child of King Frederick William I of Prussia and Princess Sophia Dorothea of Hanover.
When he was only 14, Henry was appointed as Colonel of the 35th by Frederick after he became king in 1740, leading Henry to participate in the first two Silesian Wars. Henry's conflicts with his older brother, King Frederick II of Prussia, are almost legendary. Especially when he was young, the king bullied his little brother much like his father had bullied him. Although remarkably similar in appearance and tastes (both were fond of the arts and French literature, and both were exceptional military commanders) Henry resented being in Frederick's shadow while the latter excluded his brothers from all decisions about state affairs. Nonetheless, he loyally served as one of his brother's top generals throughout Frederick's reign. His military achievements eventually earned him the respect of his brother. Henry tended to be less aggressive than the King in battle; although he never won a victory of the scale of Rossbach or Leuthen (two of Frederick's greatest victories), his caution served him well as he was never defeated on the battlefield like his brother at Kolín or Kunersdorf. Henry lived in the shadow of his older brother and sometimes criticized the king's military strategies and foreign policies, although in later years the brothers became closer. In 1753 he published his memoirs under the pseudonym "Maréchal Gessler".
On 25 June 1752, Henry married Princess Wilhelmina of Hesse-Kassel in Charlottenburg Palace, but they had no children. Henry lived in Rheinsberg Palace after receiving it as a gift from his brother in 1744 who also had a grand palace built for him in Berlin between 1748 and 1753 (today the main building of the Humboldt University of Berlin). He also had an apartment in the City Palace, Potsdam, since he was regularly present at his brother's court there and in nearby Sanssouci.
Despite the marriage, he scarcely concealed his passion for other men and developed intimate friendships with the actor Pierre-Jean Fromentin de Blainville and the French emigre Count La Roche-Aymon. From 1758, his adjutant and main favorite was Friedrich Adolf, Count von Kalckreuth, the later field marshal, but in 1766 they fell out over the prince's wife. His longtime favourite, Major von Kaphengst, exploited the prince's interest in him to lead a dissipated, wasteful life at Schloss Meseberg, an estate not far from Rheinsberg which Henry had bought for him in 1774 for which he had sold 29 paintings from his collection to Catherine the Great. In 1784, Henry had to take out a loan of 130,000 thalers in France to pay off Kaphengst's debt; King Louis XVI of France personally vouched for it. But then he separated from his lover. The king, himself presumed to have been homosexual, tolerated his brother's love affairs, sometimes even pursuing them with jealousy, but despised Kaphengst and refused his promotion to colonel whereupon the latter took his leave.