The event that led to the October Revolution of 1917 in Russia was the overthrow of the Provisional Government by the Bolshevik Party, led by Vladimir Lenin. This revolution marked the culmination of a series of events and factors that had been brewing in Russia for several years.

Russian Revolution Background:
- Socialism in Russia: Socialism had gained popularity in Russia during the late 19th and early 20th centuries as a response to the country's social and economic problems. The Marxist ideas of class struggle and the need for a proletarian revolution resonated with many Russians, particularly the working class.
- Socialism in Europe: The Russian revolution was also influenced by the wave of socialist movements and revolutions taking place across Europe at the time. The success of the Bolsheviks in Russia was seen as part of a broader global movement towards socialism.

February Revolution:
- Failure of the Provisional Government: In 1917, the monarchy in Russia was overthrown in the February Revolution, which led to the establishment of a Provisional Government. However, this government was weak and lacked popular support. It was unable to address the pressing issues facing the country, such as land reform, workers' rights, and the ongoing war effort.

Bolshevik Rise to Power:
- Vladimir Lenin: The Bolshevik Party, led by Vladimir Lenin, capitalized on the dissatisfaction with the Provisional Government and gained support through their promise of "Peace, Land, and Bread."
- Bolsheviks gain support: The Bolsheviks were able to rally the working class and the soldiers, who were disillusioned with the war and the government's inability to address their demands. They also gained support from the peasantry by promising land redistribution.

October Revolution:
- Storming of the Winter Palace: On October 25, 1917, the Bolsheviks, with the support of the Petrograd Soviet, organized an armed insurrection and seized key government buildings, including the Winter Palace, which was the seat of the Provisional Government.
- Establishment of Soviet Power: Following the overthrow of the Provisional Government, the Bolsheviks established Soviet power and formed the Russian Soviet Federative Socialist Republic. This marked the beginning of the Russian Revolution and the subsequent establishment of a socialist state in Russia.

Conclusion:
The October Revolution of 1917 in Russia was the result of a culmination of factors, including the failure of the Provisional Government, the rise of the Bolshevik Party, and the support of the working class, soldiers, and peasantry. This revolution marked a turning point in Russian history, leading to the establishment of a socialist state and paving the way for the formation of the Soviet Union.