Hitler's mistakes in 1941 included all of the following except which one?

The correct choice is the Battle of the Bulge. This is because in late 1944, during the wake of the Allied forces' successful D-Day invasion of Normandy, France, it seemed as if World War II was all but over. But, on Dec. 16, 1944 with the onset of winter, the German army launched a major counteroffensive. It was the last specific German offensive campaign in the western theater during World War II.

This counter attack was intended to cut through the Allied forces in a manner that would turn the tide of the war in Hitler's favor. So the battle that ensued is known historically as the Battle of the Bulge. Courage and fortitude of American soldiers were tested against a great adversity. Nevertheless, the quality of the response by the U.S. troops ultimately resulted in a great victory over the Germans.

Some historical sources reported that up to 19,000 Americans were killed. But General Eisenhower's personnel chief put the number at about 8,600. British historian Antony Beevor reported the number killed as 8,407. It was the largest and bloodiest battle which was fought by the United States in World War II.