On Turn 25, our heroes start off near Tula in pristine condition, with 98/99 TOE and 75 morale. They are on supply priority 3 and getting good supply, sitting in a level 2 fort. All the other German divisions nearby are similar. And overall, across the front, Axis receives 25,796 supply compared to 18,307 needed according to the logistics freight report.
Before:

0 wins, 0 losses
75 morale
98/99 TOE
16474 men
168 guns
633 ammo out of 499 needed
305 trucks out of 285 needed
But within a few short turns, by the start of Axis turn 28, it will look like this:

After:
1 win, 5 losses
66 morale
50/68 TOE
11950 men
101 guns
181 ammo out of 275 needed
138 trucks out of 120 needed
One of the most important things to note is the TOE (as well as the trucks, ammo, and morale) of the unit drops a lot more drastically than the manpower of the unit. On turn 28, the unit still has 11,950 men out of the original 16,474 men (72% of the total), but the undamaged TOE drops down all the way to 50, and the damaged TOE is 68.
If it were a Panzer division or a division with a more intricate TOE with more rare components, the difference would be even larger, with it dropping even more quickly to a very low TOE. I think the reason for this is that those rare elements (especially guns and AFVs) get disproportionately damaged and destroyed by retreat losses, as compared to manpower. Retreat losses are the predominant culprit, because pretty much whenever anything gets damaged, it then dies to retreat losses automatically just because it is damaged.
Read on to follow our unit's journey from here to there in detail...
Note - although the screenshots look like summer, it is actually winter (December), I just have weather graphics turned off.