The two entities since shared all essential experiences; they fought as part of the Balkan League when it came to removing the Ottomans from Rumelia during the First Balkan War, and they fought alongside each other against Austria-Hungary and Germany during World War I. Plans for "Serb unification", having predated the independence of the countries, were finally partially implemented after the war. The Podgorica Assembly (November 1918) concluded the decision to merge the Kingdom of Montenegro with the Kingdom of Serbia, followed by the creation of Yugoslavia. The Montenegrin monarchy was thereby removed, and opposition to the annexation culminated in the Christmas Uprising (1919) in which a smaller part the Montenegrin population demonstrated against the Serbian takeover.