The article analyzes the reaction of the Czechoslovak émigré government in London to the German attack on the Soviet Union on June 22, 1941. The author emphasizes the dependence of the Czechoslovakian émigré government on the Western allies, primarily from Great Britain, and the positive attitude towards the entry of the USSR into the war. She reconstructs the events of the first days after the start of the Great Patriotic War on the basis of documents published in Russia and the Czech Republic, shows the progress of negotiations on the restoration of Czechoslovak-Soviet relations, which ended with the signing of a political agreement on cooperation on July 18, 1941 and a military agreement on the formation of Czechoslovak military units on the territory of the USSR on September 27, 1941. The assessment of the significance of the agreements reached is given.