He was born in Peterskirchen/Oberbayern into a Bavarian family. His father was the teacher Johann Anton Rauch. He began his career in 1756 as a page at the court of the Principality of Brunswick-Wolfenbüttel and in 1761 became an engineer in the Brunswick Army. Under Charles William Ferdinand, Duke of Brunswick-Wolfenbüttel he took part in the closing phases of the Seven Years' War, namely in the 1761-62 sieges of Kassel, Meppen and Ziegenhain. In 1764 he was made a conductor in the Brunswick Engineer Corps, rising to lieutenant in 1766 and captain in 1772. On Charles William Ferdinand's recommendation, Rauch moved to the Prussian Army in August 1777. On personal instructions from Frederick II of Prussia he became a teacher at the mining corps in the Königsberg garrison. In 1788 Frederick William II of Prussia founded a Royal Engineering Academy in Potsdam - Rauch moved there and was promoted to major. The institution also took part in military surveying and so Rauch travelled to Silesia in 1791 and the Glatzer Schneegebirge in spring 1792. He also began to write treatises on military theory and to produce collections of maps. He served as a captain of guides on the Prussian General Staff during the French campaign and helped take the fortresses at Longwy and Verdun. He then caught dysentery and stayed in a hospital in Koblenz until November 1792. The king made Ruach an oberst lieutenant in 1796 and put him in charge of the Engineering Academy. He became a major general in 1805 and was made governor of Stettin on the outbreak of the War of the Fourth Coalition in summer 1806, with the 77-year-old lieutenant generalRomberg as his deputy. After the defeats in the battle of Jena-Auerstedt, Prussia's field army retreat and began to split up. Romberg's morale collapsed and when eight hundred French cavalry arrived before Stettin on 29 October 1806 he surrendered immediately without waiting to assess the size of the enemy force, which was vastly dwarfed by Stettin's garrison of 5,184. Rauch agreed to the surrender and so on 1 December was dishonourably discharged from the Prussian Army. He was later placed under house arrest and then in 1809 sentenced to life imprisonment in the Spandau Fortress. His fate led to protests within Prussia's officer corps, especially since Romberg had only ever been a scientist and lecturer and had never before commanded an army in the field. Frederick William's queen-consort Louise of Mecklenburg-Strelitz took up the cause, but she was only able to get the sentence commuted to life imprisonment in the town of Spandau rather than the fortress, though she did also get half of Rauch's pension as a major general resintated.
