The Bolsheviks in Russia are embattled, with counter-revolutionary forces threatening their rule across the country. The Czechoslovak Legion provides a particularly potent threat, controlling the Trans-Siberian Railway; working in alliance with the Komuch government in Samara they threaten to bring an end to Bolshevik rule. Vladivostok has fallen to the Legion, which they now proclaim to be an Allied protectorate. The Allies begin to think of using the port to aid anti-Bolshevik forces in Russia, with the ultimate aim of bringing the country back into the war against Germany. President Wilson goes so far as to suggest that Japan could send forces to secure Vladivostok, allowing the Czechoslovaks to redeploy further to the west.
But the Bolsheviks face other threats further to home. When the Bolsheviks seized power last November, they did so in alliance with the left faction of the Socialist Revolutionary Party (the Left SRs). However the Left SRs were not supportive of the Brest-Litovsk peace treaty with Germany, seeing it as a betrayal of the revolution. Left SR commissars resigned from Sovnarkom, the Soviet government, but the party remained broadly supportive of the soviet regime, a kind of loyal opposition. Since then they have become increasingly disenchanted by the Bolsheviks’ authoritarianism and their perception that the country is being transformed into a German client state.
Now the Left SRs decide to act. One of their activists assassinates Count Mirbach, the German ambassador, an act of propaganda by deed intended to ignite a general uprising of the masses against the Bolsheviks. When Dzerzhinsky, Lenin’s head of the Cheka (the political police), tries to arrest the murderers he is himself arrested: most members of the Cheka in Moscow are in fact loyal to the Left SRs rather than the Bolsheviks.
The Germans are understandably furious at the murder of their ambassador. Lenin is summoned to the German embassy where he issues a grovelling apology. His situation is now desperate. The Left SRs have far more armed men in the capital than he does: if they press their advantage the Bolshevik regime could find itself decapitated.
Wilhelm von Mirbach (Wikipedia)