The forts of Metz are two fortified belts around the city of Metz in Lorraine. Built according to the design and theory of Raymond Adolphe Séré de Rivières at the end of the Second Empire—and later Hans von Biehler while Metz was under German control—they earned the city the reputation of premier stronghold of the German reich. These fortifications were particularly thorough given the city's strategic position between France and Germany. The detached forts and fortified groups of the Metz area were spared in World War I, but showed their full defensive potential in the Battle of Metz at the end of World War II. Context Before the invention of rifled artillery, the place de Metz was considered untakeable. In the 19th century, improvements in artillery forced French engineers to conceive a new defensive system around the stronghold of Metz, the first fortified belt. For this work marshal Adolphe Niel allocated a sum of twelve million gold francs, used for four detached advance forts, Saint-Quentin and Plappeville to the west, and the Fort de Saint-Julien and Fort de Queuleu to the east. This measure, conceived by colonel Séré de Rivières, was incomplete when war broke out in 1870. After the Treaty of Frankfurt, the defenses of Metz were completed by German military engineers, who added seven more forts between 1871 et 1898. These forts, designed by Hans von Biehler, made up the first fortified belt of Metz. The purpose of this first belt was to hold attackers at a distance and keep them away, thus protecting the city from direct enemy fire. The forts could also assist troop maneuvers outside the fort by providing supporting fire. Because of advances in artillery technology, between 1899 and 1916 the first belt was reinforced by a second, composed of nine fortification groups. Based on new concepts of defense, such as dispersion and dissimulation, the fortification groups were intended to constitute an uncrossable barrier to any attacking French forces. The fortifications of Metz were part of a larger program of fortifications called Moselstellung which fortresses scattered between, Thionville et Metz in the Moselle valley. The German objective was on the one hand to protect against a French attempt to retake Alsace-Lorraine from the German Empire, and on the other to form an advance post in French defenses capable of serving as a rear base to a German offensive. For this major strategic point in