Leopold Hermann Ludwig von Boyen (20 June 1771 – 15 February 1848) was a Prussian army officer who helped to reform the Prussian Army in the early 19th century. He also served as minister of war of Prussia in the period 1810-1813 and later again from 1 March 1841 – 6 October 1847. Life Born in Kreuzburg (today's Slavskoye, Russia) in East Prussia, Boyen joined the army in 1784 in Königsberg. In 1788, as a newly minted second lieutenant, he took up a post in the military academy in Königsberg, where he also attended some of the lectures of Immanuel Kant. From 1794 to 1796, Boyen took part in the Polish campaign as Adjutant to General von Günther. In 1799, he became a captain. He served in the war of 1806 on the General Staff of the Duke of Brunswick, and was wounded at the Battle of Auerstädt (14 October 1806). After the Treaty of Tilsit (July 1807) he became a major and a member of Gerhard von Scharnhorst's commission for military re-organisation. By 1810 Boyen had become Director of the Military Cabinet. In the re-constitution of the Prussian army he functioned as Scharnhorst's most diligent helper, but after the conclusion of the alliance between Prussia and France in 1812 he resigned his commission as a colonel and visited Vienna and St Petersburg. The events of 1813 saw him recalled to the Prussian service: as a colonel he accompanied the Russian army from its base in Kalisz to Saxony. After the Battle of Lützen (2 May 1813) he had charge of the border guards and ultimately the defence of Berlin. But during the truce King Frederick William III named him Chief of General Staff of the 3rd Army Corps. As such, Boyen participated in the battles and skirmishes of 1813 and 1814 and gained promotion to major-general. After the first Peace of Paris (30 May 1814) Boyen took up his appointment as War Minister. He completed the setting up of the Landwehr reserve (begun during the war) and in 1818 became a lieutenant general. He struggled in vain against growing reactionary forces which endangered the broad popular base of the Landwehr, and resigned in 1819. For 21 years Boyen lived in retirement, occupying himself with historical studies, until King Frederick William IV, immediately after ascending the throne, recalled him to active service, and promoted him to general of the infantry.