Russo-Turkish War and the Congress of Berlin
Also called: Congress of Berlin, Treaty of San Stefano
Russia defeated the Ottoman Empire in the name of the Balkan Slavs, but at the Congress of Berlin, called because Britain and Austria objected, its southward advance was checked again.
Anton von Werner · Public domain · Source
When the Ottomans brutally crushed the Bulgarian uprising of 1876, Russia, championing Pan-Slavism, declared war on 24 April 1877. After the siege of Plevna the Russian army crossed the Balkan Mountains and approached Istanbul, and the Treaty of San Stefano of March 1878 created a large "Greater Bulgaria" under Russian influence.
Britain and Austria, unwilling to see Russia reach the Mediterranean, objected, and Germany’s Bismarck, posing as an "honest broker", hosted the Congress of Berlin in June–July 1878. Serbia, Montenegro and Romania won recognition of their independence, but Bulgaria was cut down to a small autonomous principality; Austria gained the right to administer Bosnia-Herzegovina, and Britain took Cyprus.
Blocked in the Balkans, Russia turned to Central and East Asia, and its rivalry with Britain (the Great Game) stretched from Afghanistan to the Geomundo incident in Korea (1885). The Balkans, where Pan-Slavism collided with Pan-Germanism, became the "powder keg of Europe".