In the study, the author analyses the legal status development of the Czechoslovak Legions in Russia in 1918; the international law context of their activities in this period. Status of the legions is characterised using the legal terms and terminology, such as: “armed neutrality” of the Czechoslovak military corps, i.e. The Legions (March to May 1918); and “armed conflict”. Four variants and factors possibly leading and contributing to the origin and escalation of the armed conflict of the Czechoslovak Legions with the Russian Soviet Federative Socialist Republic (RSFSR) in 1918 - 1920 are described.