After being called out to quell workers' demonstrations on the streets of Petrograd (now St. Petersburg), regiment after regiment of soldiers in the city's army garrison defect to join the rebels on March 12, forcing the resignation of the imperial government and heralding the triumph of the February Revolution in Russia.
The most immediate cause of discontent among the Russian people was the country's disastrous participation in the First World War. Despite enjoying success against Austria-Hungary in the first years of the war, the czar's armies had suffered repeated crushing defeats at the hands of the German army on the Eastern Front. When combined with Russia's backward economy, its repressive government and its huge population of hungry and frustrated peasants, defeat on the battlefield pushed the country into full-scale revolution in 1917.
Demonstrators took to the streets of Petrograd, the Russian capital, on March 8, 1917, clashing with police but refusing to leave the streets. By March 10, all of Petrograd's workers were on strike; the next day, the troops of the Petrograd army garrison were called out to quell the uprising.
In some initial encounters, the regiments opened fire, killing some workers; the total number killed reached about 1,500. Though the demonstrators fled after being fired upon, they refused to abandon the streets altogether and returned to confront the soldiers again. Soon, many troops began to waver when given the order to fire on the demonstrators, even allowing some to pass through their lines. On March 12, regiment after regiment defected to join the demonstrators. Within 24 hours, the entire Petrograd garrison—some 150,000 men—had joined the February Revolution, ensuring its triumph.
Three days later, Czar Nicholas II abdicated the throne in favor of his brother Michael, who refused the crown, ending the czarist regime and leaving Russia in the hands of a new provisional government, led by Russia's minister of war, Alexander Kerensky, and tolerated by the Petrograd Soviet, the worker's council formed by the February rebels. Kerensky hoped to salvage the Russian war effort while ending the food shortage and many other domestic crises. It would prove a daunting task: in April, Vladimir Lenin, founder of the radical socialist group known as the Bolsheviks, returned to Russia from exile to lead the October (or Bolshevik) Revolution and take over power of the country.