 Complete the following phrase:  In the course of these processes, by the beginning of the October Revolution, the Bolsheviks were gaining a majority, primarily in the Soviets of Workers and Soldiers Deputies of large industrial cities, gaining up to 90 of the seats in the Petrograd Soviet and up to 60 in Moscow. On September 17, 1917, the Bolshevik Viktor Nogin became Chairman of the Presidium of the Moscow Soviet; on September 25, the Petrograd Soviet was headed by Leon Trotsky. Relying on their firm majority in the Petrograd Soviet, the Bolsheviks were able, despite the opposition of the All-Russian Central Executive Committee, to convene the Second All-Russian Congress of Soviets of Workers and Soldiers Deputies and prepare for the 