The article is focused on the evolution of the traditional concepts of Russian public consciousness («Moscow the third Rome», Slavic brotherhood, liberating mission of Russia etc.) in the years of the First World War. Public reaction to the key events of the war is investigated, such as the Russian occupation of Galicia and the decision of the Entente powers to hand over Constantinople to Russia after the war. The elements of eschatology and messianism which were characteristic of the Russian consciousness, clashed with the ecclesiastical and political realities of Europe and Near East.