Frederick William III (German: Friedrich Wilhelm III., König von Preußen; 3 August 1770 – 7 June 1840) was King of Prussia from 1797 to 1840. He ruled Prussia during the difficult times of the Napoleonic Wars and the end of the Holy Roman Empire. Steering a careful course between France and her enemies, after a major military defeat in 1806, he eventually and reluctantly joined the coalition against Napoleon in the Befreiungskriege. Following Napoleon's defeat, he was King of Prussia during the Congress of Vienna, which assembled to settle the political questions arising from the new, post-Napoleonic order in Europe. He was determined to unify the Protestant churches, to homogenize their liturgy, their organization, and even their architecture. The long-term goal was to have fully centralized royal control of all the Protestant churches in the Prussian Union of Churches. Frederick William was born in Potsdam in 1770 as the son of Frederick William II of Prussia and Frederica Louisa of Hesse-Darmstadt. He was considered to be a shy and reserved boy, which became noticeable in his particularly reticent conversations distinguished by the lack of personal pronouns. This manner of speech subsequently came to be considered entirely appropriate for military officers. He was neglected by his father during his childhood and suffered from an inferiority complex his entire life. As a child, Frederick William's father (under the influence of his mistress, Wilhelmine Enke, Countess of Lichtenau) had him handed over to tutors, as was quite normal for the period. He spent part of the time living at Paretz, the estate of the old soldier Count Hans von Blumenthal who was the governor of his brother Prince Heinrich. They thus grew up partly with the Count's son, who accompanied them on their Grand Tour in the 1780s. Frederick William was happy at Paretz, and for this reason in 1795 he bought it from his boyhood friend and turned it into an important royal country retreat. He was a melancholy boy, but he grew up pious and honest. His tutors included the dramatist Johann Engel. As a soldier, he received the usual training of a Prussian prince, obtained his lieutenancy in 1784, became a lieutenant colonel in 1786, a colonel in 1790, and took part in the campaigns against France of 1792–1794. On 24 December 1793, Frederick William married Louise of Mecklenburg-Strelitz, who bore him ten children. In the Kronprinzenpalais (Crown Prince's Palace) in Berlin, Frederick William lived a civil life with a problem-free marriage, which did not change even when he became King of Prussia in 1797. His wife Louise was particularly loved by the Prussian people, which boosted the popularity of the whole House of Hohenzollern, including the King himself. Frederick William succeeded to the throne on 16 November 1797. He also became, in personal union, the sovereign prince of the Principality of Neuchâtel (1797–1806 and again 1813–1840). At once, the new King showed that he was earnest of his good intentions by cutting down the expenses of the royal establishment, dismissing his father's ministers, and reforming the most oppressive abuses of the late reign. He had the Hohenzollern determination to retain personal power but not the Hohenzollern genius for using it. Too distrustful to delegate responsibility to his ministers, he greatly reduced the effectiveness of his reign since he was forced to assume the roles he did not delegate. This is a main factor of his inconsistent rule.

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