Upon the 1809 Treaty of Schönbrunn, Napoleonic troops crossed the Plöcken Pass to occupy the Upper Carinthian lands around Villach, which had been ceded to the French Empire as part of the Illyrian Provinces. In World War I the pass became a theater of the Italian Campaign of 1915-1918, when Italian Alpini troops tried to push northwards into Carinthia, though to no avail. As both sides soon concentrated on attrition warfare, numerous bunkers and tunnels were constructed, the remnants of which are still visible today.