Bolshevik revolution occurred in 1917 whereby they seized control of Russia. In that year there were 2 revolutions and the first was in February. Russia had been going through serious turmoil.
The ww1 was a serious disaster and saw over million dead and demonstrations by the Russian people.
Corruption was rife and policies made by the Tsar were not in touch with what people wanted. The Russian army was sent less equipped and met sad fate. That was the final straw and marked the time for change.
Russia was in chaos as people began looting and rioting was happening. Members of the Russian army joined the people aswell. Finally the Tsar abdicated .
A provisional government was srt up but was ineffective. The Bolsheviks began to appeal to the masses of people and promised them food ,land etc. Then in October the Bolsheviks with other factions took control of important buildings.