In World War I Šnejdárek fought on the Western Front. He first reached the German-French frontline as a secondary troop commander on 2 August 1914, and was wounded in the First Battle of the Aisne on 21 September, earning a promotion to Captain and a citation in the army report for bravery. After his recovery he returned to the frontline on 12 February 1915, but was again wounded in the Battle of Arras four months later.