Revolutionary defeatism is a concept made most prominent by Vladimir Lenin in World War I. It is based on the Marxist idea of class struggle. Arguing that the proletariat could not win or gain in a capitalist war, Lenin declared its true enemy is the imperialist leaders who sent their lower classes into battle. Workers would gain more from their own nations’ defeats, he argued, if the war could be turned into civil war and then international revolution.
Initially rejected by all but the more radical at the socialist Zimmerwald Conference in 1915, the concept appears to have gained support from more and more socialists, especially in Russia in 1917, after it was forcefully reaffirmed in Lenin's April Theses as Russia's war losses continued, even after the February Revolution (the Provisional Government kept them in the conflict).