帝国主義論
Living in Paris and then Krakow, he focused on internal conflict within the Marxist movement, opposing the ideas of the Mensheviks and Alexander Bogdanov; he penned "Materialism and Empirio-criticism" to counter his critics. During the First World War, he relocated to Switzerland, where he argued that socialists should work toward converting that "imperialist war" into a continent-wide "civil war" in which the proletariat could overthrow the bourgeoisie. He summarised his thought in the book "Imperialism, the Highest Stage of Capitalism" and also re-interpreted Marxism on the basis of reading Hegelian philosophy. When the February Revolution of 1917 led to the abdication of the Tsar and the development of the Russian Provisional Government, Lenin returned to St. Petersburg, now called Petrograd. There, he urged the Bolsheviks to oppose the new government, and support proletariat revolution.