In September 1939 he was drafted into the army, allocated to the Army Poznan as the Head of the chemical – bacteriological field hospital No. 202. Near Kutno, the sanitary train in which the hospital was housed, was bombed. 18 September 1939 during the battle of the Bzura River, in Sennik, Dr. I. Roszkowski was wounded and taken prisoner. On 15 October 1939, thanks to the help of his uncle Wacław Roszkowski and friend, Jerzy Niżałowski, he managed to escape from the POW camp and returned to Warsaw.