In 1941, he served as Commanding Officer 6th Artillery Regiment and Chief of Staff Higher Technical Department.
After Romania entered World War II on the side of the Axis powers, Cosma participated in the Siege of Odessa.
On August 24, 1944, the day after King Michael's Coup, Cosma was taken prisoner of war by the Red Army at Târgu Neamț.
Held in captivity at Bistricioara, he was set free a month later, and he returned to serve as General Officer Commanding Artillery Mountain Corps in the struggle against Nazi Germany.
[3] In 1955 he was tried at the Military Tribunal in Iași by the Communist authorities for his role on the Eastern Front; Cosma was found not guilty and was acquitted.