There were two phases to the Revolution: the first, in March (Old Style, February, whence February Revolution), was sparked off by food and fuel shortages during the First World War and began with strikes and riots in Petrograd (St Petersburg). The tsar abdicated, and a provisional government was set up. The second phase, in November 1917 (Old Style, October, whence October Revolution), was marked by the seizure of power by the Bolsheviks in a coup led by Lenin. After workers' councils or soviets took power in major cities, the new Soviet constitution was declared in 1918