According to the Final Act of the Congress of Vienna in 1815, the Rhineland became a Prussian province. The fortification of the Koblenz area became a Prussian military priority, because of its proximity to France and the fact that Koblenz was a bottleneck for all means of transportation (ships, railways, land transportation because of bridges). Hence, the Prussians built a system of fortification around Koblenz, the so-called "Festung Koblenz" ("Fortress Koblenz"), from 1815 until 1834. This referred to the strong ring of fortifications around Koblenz, of which the Festung Ehrenbreitstein was a part. Fortress Koblenz was said to have been the largest military fortress in Europe except for Gibraltar. Ehrenbreitstein could be defended by up to 1200 soldiers.