Under the terms of the 1815 Peace of Paris, France was obliged to pay for the construction of a line of fortresses to protect the German Confederation against any future aggression by France. All fortresses were located outside Austria and Prussia — the two biggest, bickering powers of the Confederation.
Section C. "Defensive System of the Germanic Confederation" of the protocol drawn up at Paris on 3 November 1815, declared Mainz, Luxemburg, and Landau to be fortresses belonging to the Confederation of Germany, and stipulated that a fourth should be constructed on the Upper Rhine. In conformity with this act, a portion of the funds, which France was compelled to pay by way of indemnity for the cost of placing her on a peaceable footing, was thus appropriated: £200,000 were set aside for completing the works at Mainz; £800,000 were assigned to Prussia, to be applied upon its fortresses on the Lower Rhine; another £800,000 were reserved for constructing the new federal fortress on the Upper Rhine; and Bavaria was allowed £600,000 towards erecting another strong place on the Rhine, at Germersheim or some other point.[1]
By 1835 the works about Mainz were completed; the twin fortresses of Koblenz and Ehrenbreitstein, and Cologne had been abundantly strengthened on the side of Prussia; and, on the Bavarian side, the fortress of Germersheim was in a state to defend the passage on the Upper Rhine. The western frontier of Germany had, in this way, been provided with a formidable line of defences against possible hostile actions by their neighbours. The eastern side of Germany has been additionally fortified by the erection of a strong citadel at Posen; and the southern was to be still further protected by the formidable works in course of construction at Brixen in the Tyrol.[1]
The fortress of Ulm became a major strategic fortress able to accommodate 100,000 men and their equipment. Since the Kingdom of Württemberg had no engineering corps King William I appointed Moritz Karl Ernst von Prittwitz, a Prussian major, as the supervisor to oversee the building the fortresses. His plans included the provisions for the prospective development of the city Ulm. Major Theodor von Hildebrandt was appointed to oversee the building of fortresses around Neu-Ulm on the Bavarian side of the Danube.[2][better source needed]