Upon his return from China, Tkhor was transferred to the Kiev Military District where he held the position of deputy commander of the 62nd Heavy Bomber Division under the rank of major general. In May 1941, he graduated from the Military Academy of the General Staff of the Armed Forces of Russia. At the outbreak of Operation Barbarossa he took part in the defense of the Ukrainian border. His plane was shot down in a dogfight at the closing stage of the Battle of Kiev (1941), he landed behind enemy lines and was found unconscious by a German patrol. He was initially taken to the Moabit detention center where he refused to become a turncoat despite being subjected to torture. He was subsequently detained in , a prison in Nurenberg and the Flossenbürg concentration camp. During this time frame he was questioned regularly, often returning on blood soaked stretchers. He was executed by a firing squad in January 1943. Details about his captivity and death were declassified 15 years after the end of the war.