Speaking of Hitler and Napoleon, and Ozymandias may want to comment on this, they were both adventurer-conquerors who made the same strategic error of attacking Russia. Russia is simply too big to invade.
Napoleon went straight to Moscow and occupied it, believing that would crush the opposition. But the Russians simply surrounded the French army and cut off their lines of supply.
Hitler's armies were determined not to make the same mistake, so they invaded with three army groups: one North towards Leningrad, one in the same road to Moscow that Napoleon took, and one South. This way, the Russians could not surround and cut them off in any one place. But this scheme didn't work either, as it demanded more troops than the Germans could supply. In the end, the Sixth Army in the South did not have enough manpower at Stalingrad to get the job done. In the North, the Russians survived the siege of Leningrad, and held Moscow in the center. Hitler was also driven back.
Russia proved to be the fatal turning point for both men.
Well technically the Russians just kept retreating, using scorched earth tactics, even burned Moscow (or rather allowed it to happen). They didn't surround the
Grande Armee, but they did the nail the flanks pretty hard on the winter retreat. They didn't cut off the supply lines; it was simply impossible an logistical task to begin with.Interestingly, Hitler knew his history, and Barbarossa was planned for May so he didn't get caught in winter like Napoleon was. Except Mussolini mucked up the timetable; jealous of Germany's conquests, he decided to invade the Greco-Albanian frontier, and at the same time, there was a coup in Belgrade. The Fuhrer diverted resources and pushed everything back four weeks to vent his personal spite and clean up Il Duce's mess.
In the end the Germans marched on almost the same date of departure as Napoleon. Hitler's own pettiness cost him any chance of winning on the eastern front. The author of the Rise and Fall of the Third Reich labeled the delay the biggest mistake of WWII.
The Battle for Moscow gets overlooked by historians who find the massive tank battle at Kursk and the siege at Stalingrad to be more compelling. Largest battle in history - 7.5 million - with a horrendous loss of life, perhaps one third of the combatants.
Ideologically Joe and Adolf were starkly different, but what they shared in common was a complete lack of respect for humanity. The loss of millions of lives, be in 'undesirables' or their troops, meant nothing to them.