Final answer:
Lenin became the leader of the Bolshevik Party in 1903 and played a pivotal role in the Bolshevik revolution and the formation of the Soviet state.
Step-by-step explanation:
Vladimir Lenin became the leader of the Bolshevik Party in 1903. After the October Revolution in 1917, he led a coup that placed the Bolsheviks in power in Russia. Lenin played a critical role in the establishment of a one-party state and he insisted that the Bolsheviks were the true representatives of Marx's ideas. His interpretation of a vanguard party led to the Bolsheviks being a highly organized militant group able to seize power during the political turmoil of World War I. Lenin died in 1924, which eventually paved the way for Joseph Stalin's rise to power.