During this period, the Russian Empire was ruled by Tsar Alexander II, who ruthlessly suppressed the Russian revolutionary movement, leading to the increasing activities of revolutionary groups. After 1874, the terrorist forces among revolutionaries rose and tried to assassinate the tsar many times. Externally, the Russian government tried to abrogate the Treaty of Paris (1856) signed after the failure of the Crimean War. 1877 On April 24th, Russia declared war on Turkey and launched an attack from the Balkans and the Caucasus. After the Russian army entered Romania, it crossed the Danube in different places in June and July, captured Pleven, an important stronghold of the Turkish army, in June+February, 5438, and approached Constantinople, the capital of Turkey, in June+the following year 10. Turkey was forced to accept the peace conditions proposed by Russia, namely the Treaty of San Stefano. The treaty proposes the establishment of Greater Bulgaria, including Adriatic Fortress and Thessaloniki, and costs Turkey 2 1. Because this will make Russia's power in Europe sit big, and all countries strongly oppose it. Finally, 1878, the European powers held a Berlin conference in Berlin, and the Treaty of Berlin replaced the Treaty of San Stefano. Bulgaria and East Rumailia were protected by Turkey, and Turkey paid 200 million rubles, which stopped Russia's ambitions in the Balkans. 1881March 13, Tsar Alexander II was killed by members of the populist party in St. Petersburg.