This is something that everyone says is important, and should play a major role in a campaign. But it is also something which I have found most campaign commanders get easily bored with.
When I ran my first PBEM campaign I included a simple system, which I ran. In effect it meant that each corps had to halt for a full day after four days moving. Even such a simple system resulted in complaints from more than one player, who felt that as an army commander they should not have to concern themselves with supply, as that was the quartermasters problem.
Despite this I gradually developed the supply system. I felt that it was right that the player who planned his supply system should benefit over the one who just ignored it.
The player contolled the collection and issue of supply. He received one days supply for one corps for each supply depot he established. To do so he had to detach a full strength infantry brigade. So to replenish the supplies he used, a CinC would have to establish four depots (one per corps) and detach 25% of his infantry strength. Of course he could recall those brigades to the corps to fight, but he would then lose his depot.
He would also have to include which corps could draw how many days supply from which depot in his daily orders. It really surprised me how often a player forgot, or just didn’t bother, to resupply when it was possible. This is pretty typical of the approach of many of the campaign players.
The problem with this system, as pointed out by an irate player, is that it rewarded the player who ignored supply. More than one player just ordered everyone to attack everything. If he also neglected to establish supply depots he would have a numerical advantage in the fighting. If he won the first battle, this advantage would increase until he ran out of supplies and ground to a halt. However by then his opponent would probably have lost the campaign.
The basic problem is that each player had too much supply at the start of the campaign, and the penalties of running out of supply were not damaging enough.
Each commander started the campaign with four days with each corps and a further four days per corps in the depot. If he ran out of supply he lost 400 men per day until he resupplied.
A campaign phase usually lasts about 10 to 15 days. If you start with 8 days supplies, and attack aggressively, you have a good chance of destroying the other player who has detached one quarter of his infantry to establish supply depots.
So I have changed the campaign rules.
Each player starts the campaign with six days supplies
When a corps runs out of supplies it can not attack, and does not receive battle replacements
It continues to lose 400 casualties per day until resupplied
The system will still be simple, and easy to administer. But the effect on the commander who ignores resupply will be pretty drastic.
I am pretty sure that some players will ignore supply and attack, attack, attack. But they will now run out of supplies after six days instead of eight days.
I have found that results are often much different than expectations. So it will be interesting to see how these new supply rules play out.