Your lack of supply problems in summer might more be related to the too flexible automatic supply-system in ROP and to the much too generous internal supply of units for two turns. I'm currently experimenting to get some more satsifying solutions (for me personally). If the AI can't cope with it, maybe I can find a PBEM-partner?
My current impression (and it isn't really more than that) is:
Countyside-supply production
Countrysides DO offer (locally bound and ephemeral) supplies. The base supply chits (1 chit=5 supply points) offered per terrain-type and weather-type can be found in the terrain files. E.g. clear terrain in good weather will offer 4 chits = 20 supply points. This base value might then be further modified (see AGEOD-wiki) by the civilisation level (wild 50%, cleared 100%, developed=civilized in ROP? 200%), roads (road +1, major road +3), military control (exact modifications unknown, the WIA manual states that if two factions are present in a region, the supply is distributed according to their share of military control), and loyalty (AGEOD-wiki: supply-modification in %= current loyalty-level +50; so a fully loyal region will offer 150% supplies).
Hypothetical example: Bunzlau/clear terrain/rain/road/civ-level: cleared/100% under control/0% loyal
should offer you: 2 base (clear terrain in rain) +1 (road) * 1 (civ-level cleared) * 1 (?) (100% control) * 1 (0% loyal) = 3 chits = 15 supply points. So it has the potential to supply 15 elements (ca. 3 units) each turn.
Consumption of countryside-supply
But: elements only draw on countryside-supply when they're totally unsupplied at the start of the turn (i.e. internal storage empty and no full supply wagon/structure nearby).
Moreover, in order to draw on the local supply, elements have to succeed a foraging/pillaging-check. The exact factors of this check are unknown to me (WIA manual states terrain, weather, civilisation level). All I know is that there is a way to overcome this hurdle. Just give all units the "forager"-ability and reduce it's parameter from 75 to something very low, e.g. 6, so that there is only a 6% chance that an element will fail in its attempt to consume local countryside-supplies.
This is extremely important because once an element fails its foraging/pillaging-check, the region counts as "looted" and will not offer any local supplies anymore (until next spring).
I will have to do some more tests in order to find out what happens if an element succeeds its foraging-check but there is no local supply left anymore. I'm pretty sure that the regions' status is not switched to "pillaged" in this case.
Interestingly, you can also get some hints by the messages in the log at the bottom at the screen. You sometimes get the information that "Unit XY is completely unsupplied in region YX". I'm pretty sure that this message only appears when NO single element of the respective unit has successfully consumed countryside-supply. E.g. I positioned 5 elements of hussars far away from any supply source. They were completely out of supply, yet the message did not appear. I guess the reason for this was that some elements of that unit have consumed countryside-supply.
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In general, I'm much happier with a very restricted automatic-supply system (reduced its pushing distance from 30 days to 8
) and an internal supply-storage for only 1 turn, compensated by increased chances to live off the land. I find myself more looking for supplies than for the enemy, which is - after all I've been reading - quite realistic. I run out of supply much more often now, but the consequences of it are a bit less severe, since I've modified the losses due to lack of supply. You can also give some more character to different units in this way: elite infantry is pretty resistant, resembling a lower desertation rate, whereas militias should almost instantly dissolve. Battle cavalry suffers more from a lack of supply because horses get weak and die very fast without the correct fodder, plus they get eaten. Husars and light infantry get a lower attrition/desertation-rate because they have less trouble to find food and fourage for their horses, and because they should have a pretty good esprit/low desertation rate. However, strentgh-loss due to lack of supply doesn't allow for much fine-tuning since most elements only have 10 strength-points. Plus I've also decreased the combat-malus for being out of supply (in vanilla-ROP, it's 50%).
The current supply-system is just too forgiving. Soldiers didn't carry food for 30 days in their knapsacks. Flour had to be transported (by engaged subjects) to the magazines, from there to the mobile, but still very slow field bakeries (which were prime targets for the enemy!) which had to produce bread 24-7 (the extreme need for firewood was satisfied by local woods and - with force - villages). From there, the bread was transported to the army (ca. each company had a wagon for this purpose). A soldier usually received rations for 5 days at maximum. Sometimes, if cereals were requisitioned, the need for mills proved to be quite problematical. So: supply was not a matter of storage only. Supply had to be "processed" by the infrastructure (bakeries) when it was needed. Whereas flour could be stored for quite long, bread in those days was usually spoiled after 9 days. So the field bakeries had to be relatively close to the armies. Moreover, flour could be transported more easily and efficiently than bread. This complex system explains why supply was the main concern of any general. The system never really functioned well, and certainly it never functioned as flawlessly as it does right now in the game. My goal is to tweak the game to represent the problems that real generals were facing. The question of local supplies and effects of lack of supplies is quite important in this regard. Generals were splitting up their forces simply because a concentration of too many men could not be supported. And indeed, "ausfouragieren", that is to forage a region before the enemy can, was a viable tactic to stop the enemy from advancing if his magazines were too far away.
