The Congress of Vienna (1815) established the new Grand Duchy and regulated the administration of the country and the Fortress. The coexistence of a Prussian garrison comprising 6,000 officers and men with a population of 4,000 Luxembourg nationals inside the Fortress led to some confusion, in a country with around 200,000 inhabitants, placed under Dutch authority. Furthermore, an indigenous federal contingent (1,000 men) was stationed at Diekirch and Echternach.

The garrison was an important economic factor in the burgeoning city. Although there were marriages between soldiers and Luxembourg citizens, the imbalance of the urban population led to clashes between civilians and soldiers.

The fortifications were restored and modernised. Alongside the new barracks, hospital and military buildings within the Fortress, the forts in the outer girdle (Thüngen) became inhabited and were reinforced. Like Mainz, Landau, Rastatt and Ulm, Luxembourg became a fortress of the German Confederation. Because of its exposed position on the border to France, it was held in considerable esteem, which was illustrated by the princely origins of its governors. The railways required the construction of modern forts (Wedell). However, the Fortress lost its strategic edge with the advent of new artillery techniques.

Following the Belgian Revolution, the Treaty of London in 1839 established the current borders of the Grand Duchy. The French-speaking part was ceded to Belgium as Province du Luxembourg. In fact, the Luxembourg population seemed to be more attracted by the prospect of the new Belgian state and many chose to move to the other side of the border.  The Bitbourg region had already been annexed to Prussia in 1815. 

-

- - - - -

- - - - - - -

- - - - - - -