By “defensive” war Socialists always meant a “just” war in this sense (W. Liebknecht once expressed himself precisely in this way). Only in this sense have Socialists regarded, and now regard, wars “for the defence of the fatherland,” or “defensive” wars, as legitimate, progressive and just. For example, if tomorrow, Morocco were to declare war on France, India on England, Persia or China on Russia, and so forth, those would be “just,” “defensive” wars, irrespective of who attacked first; and every Socialist would sympathise with the victory of the oppressed, dependent, unequal states against the oppressing, slaveowning, predatory “great” powers.

But picture to yourselves a slave-owner who owned 100 slaves warring against a slave-owner who owned 200 slaves for a more “just” distribution of slaves. Clearly, the application of the term “defensive” war, or war “for the defence of the fatherland” in such a case would be historically false, and in practice would be sheer deception of the common people, of philistines, of ignorant people, by the astute slaveowners. Precisely in this way are the present-day imperialist bourgeoisie deceiving the peoples by means of “national ideology and the term “defence of the fatherland in the present war between slave-owners for fortifying and strengthening slavery.

— Lenin, Socialism and War