Hello Parsifal
I'd say cool down. During advance, German infantry was capable to march while following motorized troops 50km per day so it should be possible in retreat 40km per day in good conditions. Of course in good blizzard nobody moved much not even Soviets and when thawn set in Soviets had an advantage but it also hindered them, so IMHO at those conditions their advance speed was lower than max they achieved. And on Russian roads, I have experience on those and even tracks.
Juha
Im fine, no need to cool down, but thanks for the concern. I would really like to know where your source for 50 km per day for an advance comes from and 40km for a retreat, and what good conditions represents. Are you saying that german Infantry, on a sustained basis, in engaged condition can advance 50km. Thats amazing, I never knew they were such invincible supermen.....that means they are marching at a rate of about of about 5kph sustained, as well as fighting...each and every day....even SAS can only advance at half that rate over broken terrain. Amazing........
My main source for my information is
TM101-10, The US Army Staff officers Field Manual (1941). It was published by the Army as the "Bible" for the army, and provided Staff Officers with a Field Manual, for the Organization, Technical,
and Logistical Data on nearly all US Army field operations. In the preamble it says "This manual and FM 101-5, Staff Officers' Field Manual The Staff and Combat Orders, are compilations of information and data to be used as a guide for the operations in the field of the general staff or a similar staff group of all units in peace and war".
Chapter 2, pages 79-148, you will obtain the relevant data for field marches. The material is detailed and meticulous, and entirely consistent with how I was trained. In fact the computations and values are similar to the british model, as inferred in the British Army Regulations, entitled
Infantry Training Manual -1937
However a basic summary is set out below, in the context of this discussion
According to US Army doctrine, the average rate of march for trained infantry under favorable weather conditions is 2-1/2 mph over roads and 1 mph cross country. A normal foot march covers 12-20 miles per day. But thats under conditions of disengagement, and assumes clear weather, and full visibility. For conditions of night, or if the formation is in contact with the enemy, or the terrain is more broken, or wooded, the march rates are about half that (typically). According to the US manual, infantry travelling on foot, over open country, which is what should be assumed for Russian conditions (and Ive been there too, incidentally) in an unengaged state, the expected sustained rate of movement for unengaged leg Infantry in 1941 was 12-15 miles per day, but for enaged Infantry, or wher difficulties might be expected, the average rate was about half that rate, or, in metric terms, about 10-15 kms per day. If you try to push your Infantry much above that your sickness rates will go up, typically for example, in unengaged conditions if you increase the march demands to say 20 miles per day (30km per day), you are statistically going to force onto the sick list, about 5% of your Infantry every day that that occurs....if the forced marching continues for more than three days, your attrition rate will double for every three day period after that. Since the situation is a retreat, with the enemy assumed to be applying maximum pressure on your forces, any men reported as unfit, will basically be lost.
I think the mistake you are making is that you are measuring performance on that applicable to a single man or small group on a hiking holiday, with regular rest stops, hot and/or regular meal stops and light loads to be carried. In wartime we are looking at large groups of men, irregular meal breaks, poor rest stops, intermittent combat, and relatively heavy loads being carried. These factors will all have an effect, and are worked out for us in TM101-10.
For the Germans, they did, on isolated occasions, achieve rates of advance of 30km per day for their Infantry. This happened in Belgium in the advance to Antwerp, but it was only over a two day period. By contrast, the leg Infantry following Gp Kleist through the Ardennes took (from memory) 5 days to cover the roughly 50 kms to the front, and that was unengaged. Similar examples can be found in 1941, in the East, but each time their Infantry performed those feats, they either needed rest or they accepted casualties from fatigue. Not as serious when you are atacking, but almost certain to lead to a more serious casualty list when retreating. After Smolensk, for example, the Infantry formations attached to AGC were reporting Infantry strengths of about 40%, on average.....German Infantry formations had fought so hard, and advanced so far, and were exhausted by that time.....it was reported the Heersgruppe to Hitler that it would take the Infantry 6 weeks to recover, so to keep the pressure on the Soviets, he ordered his panzers south in an ill-considered decision.
If we widen our search somewhat, the most celebrated sustained march rate that I know of comes from the napoleonic era, where in the lead up to Austerlitz (I think) the Guard is reported to have marched 70miles in two days,and then gone straight into battle. We do not know how many men had fallen out due to fatigue, or how long they were given to recover, but it does show that in isolatred instances in conditions of being unengaged, it might be possible for a few units, on a very tempoorary basis to reach the march rates you are suggesting