The Left Social Revolutionary party, which had been collaborating with the Bolsheviks, declared the treaty a betrayal of the cause of the revolution and withdrew from the government. Relying upon their traditional methods of political struggle, the Left Social Revolutionaries assassinated the German ambassador in Moscow, in the vain hope of stirring the Germans to renew hostilities. They also made attempts on the lives of several Bolshevik leaders. Lenin was severely wounded by one of the terrorists, receiving an injury that contributed to his early death. The Bolsheviks, in return, launched the so-called Red Terror, suppressing the Left Social Revolutionary party and executing many political opponents. Other minority parties and factions were gradually eliminated by the Bolsheviks, and the Soviet Union emerged as a one-party state.

Civil War

Bolshevik political, economic, and social policies led to civil war and foreign intervention. In Siberia, a force of 45,000 Czech former prisoners of war, who had been armed by the tsarist government to fight against Germany, launched a campaign against the Soviet authorities. Murmansk and Arkhangel'sk, the principal cities of Russia's far north, were occupied by Allied forces. Japanese forces occupied Vladivostok, and an American expeditionary force landed in that city. White Russia (an area approximately equivalent to present-day Belarus), the Ukraine, and the Caucasus were occupied by the Germans. In the autumn of 1918 Admiral Aleksandr V. Kolchak, commanding a large anti-Bolshevik force, proclaimed himself "supreme ruler of Russia" and established his capital at Omsk in Siberia. Early in 1919 a powerful attack on the Soviet forces was launched from the Ukraine by a large White (that is, anti-Bolshevik) army commanded by General Anton I. Denikin. Another White army, under General Nikolay N. Yudenich, advanced on Petrograd (now St Petersburg). Despite a series of initial reverses, the Bolsheviks succeeded in repelling these attacks by early 1920. In April of that year a new campaign was launched by the Polish army, with some help from Belorussian troops commanded by Baron Pyotr N. Wrangel. Two months later the Soviet forces, which had been reorganized and renamed the Red Army early in 1918, began a counter-offensive. The war with Poland ended with the signing in March 1921 of the Treaty of Riga, by which certain western areas of White Russia and of the Ukraine were ceded to Poland.