text: Katte affair Soon after his relationship with Keith ended, Frederick became close friends with Hans Hermann von Katte, a Prussian officer several years older than Frederick who became one of his boon companions and may have been his lover. After the English marriages became impossible, Frederick plotted to flee to Britain with Katte and other junior army officers. While the royal retinue was near Mannheim in the Electorate of the Palatinate, Robert Keith (Peter Keith's brother and one of Frederick's companions) had an attack of conscience when the conspirators were preparing to escape and begged Frederick William for forgiveness on 5 August 1730. Frederick and Katte were subsequently arrested and imprisoned in Küstrin. Because they were army officers who had tried to flee Prussia for Britain, Frederick William accused the pair of treason. The king briefly threatened the crown prince with execution, then considered forcing Frederick to renounce the succession in favour of his brother, Augustus William, although either option would have been difficult to justify to the Imperial Diet of the Holy Roman Empire. The king condemned Katte to death and forced Frederick to watch his beheading at Küstrin on 6 November; the crown prince fainted just before the fatal blow.
  Frederick was granted a royal pardon and released on 18 November 1730, although he remained stripped of his military rank. He was forced to remain in Küstrin and began rigorous schooling in statecraft and administration for the War and Estates Departments. Tensions eased slightly when Frederick William visited Küstrin a year later, and Frederick was allowed to visit Berlin for his sister Wilhelmine's marriage to Margrave Frederick of Bayreuth on 20 November 1731. The crown prince returned to Berlin after finally being released from his tutelage at Küstrin on 26 February 1732 on condition that he marry Elisabeth Christine of Brunswick-Bevern.
  Marriage and War of the Polish Succession