The 1917 Russian Revolution was not, as many people suppose, one well organised event in which Tsar Nicholas II was overthrown and Lenin and the Bolsheviks took power. It was a series of events that took place during 1917, which entailed two separate revolutions in February and October (with a great deal of political wranglings inbetween), and which eventually plunged the country into Civil War before leading to the founding of the Communist State.
The first major event of the Russian Revolution was the February Revolution, which was a chaotic affair and the culmination of over a century of civil and military unrest. The causes of this unrest of the common people towards the Tsar and aristocratic landowners are too many and complicated to neatly summarise, but key factors to consider were ongoing resentment at the cruel treatment of peasants by patricians, poor working conditions experienced by city workers in the fledgling industrial economy and a growing sense of political and social awareness of the lower orders in general (democratic ideas were reaching Russia from the West and being touted by political activists). Dissatisfaction of the proletarian lot was further compounded by food shortages and military failures. In 1905 Russia experienced humilating losses in the Russo-Japanese war and, during a demonstration against the war in the same year, Tsarist troops fired upon an unarmed crowd - further dividing Nicholas II from his people. Widespread strikes, riots and the famous mutiny on the Battleship Potemkin ensued.
Such was the climate in 1905 in fact that Tsar Nicholas saw fit, against his will, to cede the people their wishes. In his October Manifesto, Nicholas created Russia's first constitution and the State Duma, an elected parliamentary body. However Nicholas's belief in his divine right to rule Russia meant that he spent much of the following years fighting to undermine or strip the Duma of its powers and to retain as much autocracy as possible. (Modern historians might note that Russian rulers haven't come a long way in the last hundred years!).
