The overwhelming cause of the Russian Revolution of 1917 was the inefficiency and failure of the czarist regime in the World War I military effort. This was exacerbated by corruption in the government and a scarcity of food that caused riots to break out first in the capital city of Petrograd and then in other cities.
Poorly equipped and poorly led, the Russian army suffered defeat after defeat at the hands of the Germans. When the czar took personal control of the war in 1915, the continuing catastrophic losses were blamed on him. Russian common people resented seeing so many young men and horses being sent off to the disastrous front line.
The czar of Russia, Nicolas II, believed in an autocratic government and ignored or disbanded the Russian parliament, the Duma, whenever it suited him. His incompetence in governing and modernizing Russia led to a widening gap between the czarist regime and the growing urban workforce. When food riots and strikes erupted in Petrograd, the czar responded with military force against the 200,000 protesters. After initially firing on the demonstrators, the army mutinied, joined them and armed them. By mid-March, Nicholas II abdicated his throne, leading to a provisional government and eventually to Soviet rule.