Operation Barbarossa was probably the largest land campaign ever waged. It is possible that the Han invasion of the Yangste valley in the 13th century was larger, but there is no way yet to know for sure and history clouds granular detail. The attack from the Ardennes forest to the port of Antwerp was just over 200 miles. But from the German staging line to Moscow was more like 700 miles. The German staging line at the beginning of the war was over 800 miles long. Thirty supply trains were needed a day behind Army group Center under the command of Von Bock. Thirty train loads a day was just a third of the logistical requirements for the entire invasion force of over 4 million.
Just the territory to hold down in the staging area on day one amounted to 370,000 square miles. The further the Germans advanced into Russia, even under ideal conditions, the harder it would be to manage the supply line. Hitler estimated that it would only take five months to crush Russia. Perhaps that’s why Wehrmacht Chief of staff Alfred Jodl thought issuing Winter clothing would send the wrong message.
Of course the inaugural battle, the vast German kesselschlachten ( encirclements) resulted in 300,000 Russia POWs captured in the first week. The auspicious start emboldened Hitler to play it rashly. He did, allowing panzer divisions to outpace infantry until they were separated. The Germans thought the Soviets had about 190 divisions. The Soviets had 360 divisions. And of course there was absolutely no contingency plan in case everything didn’t fall precisely where it should.
By September 30, Barbarossa was essentially over. 200 Russian divisions were destroyed and 3 million prisoners were taken. It looked like a devastating loss, especially on paper. Hitler watched the winter war between Russia and Finland in 1939 and watched 50,000 Finnish hunters shoot the shit out of a million Red Guard. He commented that “once we kick the door in, the whole rotten thing will come crashing down”. This is an example of a bigot shooting himself in the foot, assuming that his betes noires cannot hold their own, cannot organize, cannot make effective weapons, etc.
The Western most Russians defending the borders of Poland garrisoned in the stretch between the Black Sea and the Baltic Sea were unprepared for a blitzkrieg. Many of the huge Russian troop formations were led by officers too junior to command; many of them who inherited the commands because the purges Stalin executed in the late nineteen thirties also mundified the Red Guard of its most experienced commanders. And Stalin could not fathom that the Germans would attack him at this time. He thought initial reports of attacks against Russian formations were an exaggeration, imagined by old Russian soldiers and trigger happy border guards.
By September, the Germans had almost a half million casualties. Again the progress was fast and the elegiac tones in commanders who spoke of the Russian plight painted a victorious picture of the outcome well ahead of schedule. Troop losses by December 1941 put the invading Wehrmacht forces at 2/3rds of the strength they had in June.
Then on December 7th, another small set back occurred that Hitler had perhaps not anticipated: Pearl Harbor.
Source: Kursk: The Greatest Tank battle. MK Barbieri. MBI 2002.