Conversation so far:
who are released and armed in the Russian Revolution events of september 1917?
The Bolsheviks were released and armed in the Russian Revolution events of September 1917
who freed the Bolsheviks in the Russian Revolution events of September 1917?
Petrograd Soviet
why were the Bolsheviks freed in the Russian Revolution events of September 1917?
influence over railroad and telegraph workers proved vital in stopping the movement of troops
what happened after the Petrograd Soviet freed the Bolsheviks in the Russian Revolution events of September 1917?
After the Petrograd Soviet freed the Bolsheviks, Trotsky became chairman of the Petrograd Soviet

Question: who was Trotsky?
Self-contained rewrite: who was Trotsky in the Russian Revolution events of September 1917?