In 1914, he joined the rifle unit of the Polish Legion, and donated his manor house in Zembrzyce for the convalescence of wounded soldiers. It was during this time that he adopted "Zyndram" (raven) as his middle name. He initially fought under the command of Captain Zbigniew Dunin-Wasowicz, then worked at staff headquarters for the Polish Legion. In 1915, he was transferred to the command of then Lieutenant-Colonel, Edward Rydz-Śmigły; participating in the battles of Jastków, Kostiuchnówka, and several others. In 1916, he fell ill with typhus. Although he recovered, this ended his active participation in the war so, in 1917, he returned to Kraków and became involved in organizing the military museum. He was promoted to captain in 1918, worked in the propaganda department of the 2nd Rifle Division, and lectured at the Military Geographical Institute. He served until 1922, when he was transferred to the reserves.