 Complete the following phrase:  In the long-run, tensions between Russia and Austria-Hungary intensified, as did the nationality question in the Balkans. The Congress succeeded in keeping Istanbul in Ottoman hands. It effectively disavowed Russias victory. The Congress of Berlin returned to the Ottoman Empire territories that the previous treaty had given to the Principality of Bulgaria, most notably Macedonia, thus setting up a strong revanchist demand in Bulgaria that in 1912 led to the 