The Military Program of the Proletarian Revolution – Lenin
This work of Lenin’s is an important read. It clarifies the important differences between revolutionary wars and reactionary, predatory wars, stressing that Marxists are not opposed to all war. The vital question is the following: “in whose class interests is any given war being waged?” Lenin notes that every oppressor class in history has been armed against the oppressed, and that it would not be possible to use strictly peaceful means to overthrow an oppressor class. He also elaborates on fighting opportunism in every field of proletarian politics.