For much of the war, Hengl was stationed on the Arctic front against the Soviet Union. Initially he commanded the 137th Gebirgsjager Regiment, receiving the Knight's Cross of the Iron Cross in August 1941. From March 1942 to October 1943 he commanded the 2nd Mountain Division, and then the XIX Mountain Corps until April 1944. In February 1945 he was designated to take over command of LIX Army Corps on the Eastern Front, but he did not take up the post.