In the 1870s, Russian nationalist opinion became a serious domestic factor in its support for liberating Balkan Christians from Ottoman rule and making Bulgaria and Serbia quasi-protectorates of Russia. From 1875 to 1877, the Balkan crisis escalated with the rebellion in Bosnia and Herzegovina, and insurrection in Bulgaria, which the Ottoman Turks suppressed with such great cruelty that Serbia, but none of the West European powers, declared war. In early 1877, Russia came to the rescue of beleaguered Serbia when it went to war with the Ottoman Empire of 1877–1878. Within one year, Russian troops were nearing Constantinople, and the Ottomans surrendered. Russia's nationalist diplomats and generals persuaded Alexander II to force the Ottomans to sign the Treaty of San Stefano in March 1878, creating an enlarged, independent Bulgaria that stretched into the southwestern Balkans. Another significant result of the 1877-78 Russo-Turkish War in Russia's favour was the acquisition from the Ottomans of the provinces of Batum, Ardahan, and Kars in the South Caucasus, which were transformed into the militarily administered regions of Batum Oblast and Kars Oblast. To replace Muslim refugees who had fled across the new frontier into Ottoman territory the Russian authorities settled large numbers of Christians from an ethnically diverse range of communities in Kars Oblast, particularly the Greek Orthodox Georgians and Caucasus Greeks, and Christian but mainly non-Orthodox Armenians, all of whom hoped to achieve their own regional ambitions on the back of the Russian Empire. When Britain threatened to declare war over the terms of the Treaty of San Stefano, an exhausted Russia backed down. At the Congress of Berlin in July 1878, Russia agreed to the creation of a smaller Bulgaria. Russian nationalists were furious with Austria-Hungary and Germany for failing to back Russia, but the Tsar accepted a revived and strengthened League of the Three Emperors as well as Austro-Hungarian hegemony in the western Balkans.