Before I write anything I should qualify that I'm a layman on modern military history, I just like reading about it.

The German Landser during Operation Barbarossa might have had to walk up to 40 miles a day, but more usually marched 20 (Stalingrad 32). They carried forty five pounds of equipment (32), which in the grand scheme of things is normal for well trained soldiers.* They were also desperate to complete their strategic offensive to avoid being stuck in the open in the winter (Stalingrad 39, 43). That said, the soldiers had to maintain these paces for weeks at a time and potentially fight at points, and they were apparently so tired that they often fell asleep on the march (Stalingrad 32). The German army had faced the perils of pushing their troops too hard before: at the climax of the Schlieffen Plan's execution in 1914, some German infantry had to fight the catastrophic Battle of the Marne after having marched 400 miles in less than a month, and by the end of the battle had been fighting continuously for nine days (Hastings, 339). That said, if anybody could do it, was the ultra-motivated and extremely fit troops of the Wehrmacht in 1941.

The winter and season of rain and mud (rasputitsa) that began in October was what really hit the German foot-sloggers hard (Stalingrad 36). Once roads bogged down, vehicles using these roads were probably often slower than infantry (Stalingrad 36, also Ardennes 171, 178) Temperatures dropped to -20 degrees (centigrade), soldiers had to light fires under the engines of vehicles before they could try to start them, and machine guns and radios froze solid (241-2). The Landser had to warm the ground with a fire before he could dig a trench or shellscrape, their jackboots were falling apart and could not easily be replaced, they had a shortage of gloves and they had to take winter clothing from civilians, which apparently caused some Officers to complain that their soldiers looked more like Russian peasants than German infantry (242). They sawed the legs off the dead and thawed them over fire to pull off the boots, and piles of frostbitten limbs could be found outside field hospitals (283). German soldiers attempted to strip Russians soldiers while they were still warm so their jackets didnt freeze (284). Suicides skyrocketed (Stalingrad 45). During this first winter frostbite casualties began to exceed battle casualties,** which were themselves very high: the Wehrmacht had suffered 400,000 casualties by the end of August (only a couple of months: see Stalingrad 31), compared to 150,000ish casualties in the campaign against France. Of course, even these latter numbers are outlandishly huge compared to anything a 21st century army would ever expect to deal with.

*Roman legionaries often carried 50-60 pounds. See Jonathan P. Roth, The Logistics of the Roman Army at War (264 BC- AD 235), Boston: Brill, 1999, 115. At times they also had to cover significant distances and perform at the end of the march: Caesar marched his troops 25 miles and immediately threatened an enemy force into submission (Gallic Wars 7.40), and if I recall at one point he stormed a city immediately after a forced march, though I can't recall the citation right now.

**By Christmas, German frostbite casualties had reached about 100,000 (Stalingrad 40).

Sources:

Beevor, Stalingrad, 1998.

Beevor, The Second World War,

Beevor, Ardennes 1944: Hitler's Last Gamble , 2015.

Max Hastings, Catastrophe: Europe Goes To War 1914, 2013.

-Hopefully it doesn't bother anybody that I use Beevor a lot.