This collection is the first scientific two-volume publication on the history of Czech-Slovak (Czechoslovak) national military units in Russia. The first volume of the collection includes documents of Russian and Czech archives for the period of the First World War and the beginning of the Civil War. For the first time, documents of the military, foreign policy and other departments of the Russian Empire, as well as public bodies of leadership of the Czech-Slovak national movement in Russia, are being introduced into scientific circulation.