On June 22, 1941, Adolf Hitler launched his armies eastward in a massive invasion of the Soviet Union: three great army groups with over three million German soldiers, 150 divisions, and three thousand tanks smashed across the frontier into Soviet territory. The invasion covered a front from the North Cape to the Black Sea, a distance of two thousand miles. By this point German combat effectiveness had reached its apogee; in training, doctrine, and fighting ability, the forces invading Russia represented the finest army to fight in the twentieth century. Barbarossa was the crucial turning point in World War II, for its failure forced Nazi Germany to fight a two-front war against a coalition possessing immensely superior resources. In late 1942, as Hitler and Zeitzler pondered the looming disaster, Manstein seemed their only hope. On November 20, they summoned the general from the Leningrad front and put him in charge of a new formation, Army Group Don. The campaign Manstein would fight would be a lesson in how a genius can impose his will on a battlefield. In the course of this most difficult conflict, Manstein’s improvisation would overcome seemingly impossible obstacles and prove that in war one man really can make a difference. But he would also find himself a prisoner of his strategic situation, reminded that even a brilliant commander has limits.