Frederick II (German: Friedrich II.; 24 January 1712 – 17 August 1786) was a King in Prussia (1740–1772) and a King of Prussia (1772–1786) from the Hohenzollern dynasty. In his role as a prince-elector of the Holy Roman Empire, he was also Elector of Brandenburg. He was in personal union the sovereign prince of the Principality of Neuchâtel. He became known as Frederick the Great (Friedrich der Große) and was nicknamed Der Alte Fritz ("Old Fritz").
Interested primarily in music and philosophy and not the arts of war during his youth, Frederick unsuccessfully attempted to flee from his authoritarian father, Frederick William I,
with childhood friend Hans Hermann von Katte, whose execution he was forced to watch after they had been captured.
Upon ascending to the Prussian throne, he attacked Austria and claimed Silesia during the Silesian Wars, winning military acclaim for himself and Prussia. Near the end of his life, Frederick physically connected most of his realm by conquering Polish territories in the First Partition of Poland.
Frederick was a proponent of enlightened absolutism. For years he was a correspondent of Voltaire, with whom the king had an intimate, if turbulent, friendship. He modernized the Prussian bureaucracy and civil service and promoted religious tolerance throughout his realm. Frederick patronized the arts and philosophers, and wrote flute music. Frederick is buried at his favorite residence, Sanssouci in Potsdam. Because he died childless, Frederick was succeeded by his nephew, Frederick William II of Prussia, son of his brother, Prince Augustus William of Prussia.

Youth
Frederick was born in Berlin, the son of King Frederick William I of Prussia and Sophia Dorothea of Hanover. The so-called Soldier-King, Frederick William had developed a formidable army and encouraged centralization, but was also known for his authoritarianism and temper.
Sophia, on the other hand, was well-mannered and well-educated. Her father, George, Elector of Hanover, was the heir of Queen Anne of Great Britain. George succeeded as King George I of Great Britain in 1714.
The birth of Frederick was welcomed by his grandfather with more than usual pleasure, as two of his grandsons had already died at an early age. Frederick William wished his sons and daughters be educated not as royalty, but as simple folk.
He had been educated by a Frenchwoman, Madame de Montbail, who later became Madame de Rocoulle, and he wished that she educate his children.
Frederick was brought up by Huguenot governesses and tutors and learned French and German simultaneously. In spite of his father's desire that his education be entirely religious and pragmatic, the young Frederick, with the help of his tutor Jacques Duhan, procured for himself a three thousand volume secret library of poetry, Greek and Roman classics, and French philosophy to supplement his official lessons.[2]
Although Frederick William I was raised a devout Calvinist, he feared he was not of the elect. To avoid the possibility of Frederick being motivated by the same concerns the king ordered that his heir not be taught about predestination. Although he was largely irreligious, Frederick adopted this tenet of Calvinism, despite the king's efforts. Some scholars have speculated that the crown prince did this to spite his father.
Crown Prince
In 1732, Queen Sophia Dorothea attempted to orchestrate a dual marriage of Frederick and his sister Wilhelmina with Amelia and Frederick, the children of her brother, King George II of Great Britain. Fearing an alliance between Prussia and Great Britain, Field Marshal von Seckendorff, the Austrian ambassador in Berlin, bribed Field Marshal von Grumbkow and Benjamin Reichenbach, the Prussian Minister of War and Prussian ambassador in London, respectively. The pair discreetly slandered the British and Prussian courts in the eyes of the two kings. Angered by the idea of the effete Frederick being so honored by Britain, Frederick William presented impossible demands to the British, such as Prussia acquiring Jülich and Berg, leading to the collapse of the marriage proposal.[4]
Frederick found an ally in his sister, Wilhelmina, with whom he remained close for life. At age 16, Frederick had formed an attachment to the king's 13-year-old page غلام يعمل في خدمة فارس وصيف, Peter Karl Christoph Keith. Wilhelmina recorded that the two "soon became inseparable. Keith was intelligent, but without education. He served my brother from feelings of real devotion, and kept him informed of all the king's actions."
When he was 18, Frederick plotted to flee to England with Katte and other junior army officers. While the royal retinue was near Mannheim in the Electoral Palatinate, Robert Keith, Peter's brother, 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 Great Britain, Frederick William leveled an accusation of treason against the pair.
The king threatened the crown prince with the death penalty, 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 Reichstag of the Holy Roman Empire.
The king forced Frederick to watch the decapitation of his confidant Katte at Küstrin on 6 November, leaving the crown prince to faint away and suffer hallucinations for the following two days.
Frederick was granted a royal pardon and released from his cell on 18 November, although he remained stripped of his military rank. Instead of returning to Berlin, however, he was forced to remain in Küstrin and began rigorous schooling in statecraft and administration for the War and Estates Departments on 20 November. Tensions eased slightly when Frederick William visited Küstrin a year later, and Frederick was allowed to visit Berlin on the occasion of his sister Wilhelmina'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