The Decline and Fall of The Romanov Dynasty.
World War 1 was the defining factor which led to the collapse of the Romanov Dynasty in February, 1917. Without it a revolution would not have happened at this point in time. This is not to say a revolution would not have eventually happened, as many of the ingredients needed were already present. However, what World War 1 essentially did was to heighten discontent throughout society enough for it to revolt.
Russia had been experiencing major problems, both social and economic, long before war broke out in 1914. .
Social freedom was basically unheard of for the vast majority of lower-class Russians (around 50 million at the time of emancipation) and all throughout the history of Imperial Russia's there have been massive class divides. Up until the Edict of Emancipation, instituted by Tsar Alexander I in 1861, slavery (in the form of serfdom) was completely legal and actively encouraged. These serfs had practically no rights and could be sold and traded at their master's discretion. This goes to highlight the massive class divide between the landowners (extremely rich) and the serfs (extremely poor) as well as the backwardness of Russian society as compared to other European powers at the time. Even after these serfs were emancipated and given basic human rights, very little actually changed in their way of life and they were forced to pay excessive land taxes (redemption payments) or leave their homes. Subsequently two new social groups emerged in Russia, the proletariat (industrial workers who were mainly peasants that had drifted into the cities in search of work) and the bourgeoisie (capitalists and the owners of the factories). These two groups inhabited the major cities of Russia and pioneered her industrial revolution, decades after other nations such as France, England and Germany had begun theirs. The proletariat were over-worked, under-paid, suffered poor living conditions and were thus discontent with their lives.