Czechoslovak Legion
On 14 October 1916 Janoušek transferred to the Czechoslovak Legion as a private and joined its 1st Rifle Regiment at Boryspil. In 1917 after the February Revolution the Czechoslovak Legion became part of the Russian 7th Army. Janoušek fought at the Battle of Zborov on 1–2 July 1917. He was wounded on 18 July, in hospital until August and then promoted to warrant officer.