sentences:  During World War I Balabán joined the Czechoslovak Legions in Russia.Later, he served as an artillery officer in the Czechoslovak Army, then as a staff officer and at the Ministry of Defense (reaching the rank of lieutenant-colonel).After Germany occupied the remainder of Czech lands in March 1939, Balabán started to cooperate with the resistance group Obrana národa ("Defense of the nation") that had been organized by former army officers.