The First World War forced the Russian intelligentsia to rethink its values—values that had been constructed in the nineteenth century. Distancing itself from pacifism and cultural relativism, it began to search for a moral meaning to the war that broke out in 1914—i.e. to defend the war as morally right and having a higher spiritual purpose. Russian philosophers were central to these debates, as they tried to interpret the war, and the relationship between war and peace, from a metaphysical point of view. The paper will look at philosophical, ethical and religious aspects of these debates, and some of the philosophers who participated in them.