At this critical juncture , Hitler assumed personal control of the Wehrmacht high command , and his personal failings as a military commander arguably contributed to major defeats in the spring of 1943 , at Stalingrad and Tunis in North Africa . At this critical juncture , Hitler assumed personal control of the Wehrmacht high command , and his personal failings as a military commander arguably contributed to major defeats in early 1943 , at Stalingrad and Tunis in North Africa .