That works out to a bit more than 2 gp per month per soldier. Given that it is only covering supplies and no other costs of living (which are subsumed into the soldier’s wages), that seems pretty reasonable to me.
D@W assumes that 8lb of bread costs 1 silver piece (.1gp). 4 pints of water costs 1 copper piece (.01gp).
D@W further assumes a soldier needs 3lb of food and 4 pints of water per day.
3 x (.1/8) = .0375gp per day
(4/4) x (.01) = .01gp per day.
Total cost per day = .0475gp
Total cost per week = .0475gp x 7 = .3325
Total cost per 120 soldiers = 39.9gp
D@W assumes 1 pack animal per 50 men to carry tents, weapons, gear, spare equipment, flags, etc. (Based on Roman Army logistics). Each pack animal needs 20lb of food and 64 points of water per day.
20 x (.1/8) = .25gp per day
(64/4) x (.01) = .16gp per day
Total cost per day = .41gp
Total cost per week = .41gp x 7 = 2.87gp
Total cost per 120 soldiers = 2.87 x 120 x (1/50) = 6.88gp
So that suggests that supply cost should be 39.9gp + 6.88gp, or about 47gp per week per unit.
HOWEVER in certain terrain, pack animals and soldiers can drink free-standing water, so that should be reduced from the cost. And in the best terrain the pack animals can forage and that really reduces the cost.
HOWEVER we need to factor in that a large number of pack animals required to bring the food and water to the soldiers. The number of pack animals required is based on (a) the distance traveled and (b) whether the unit needs water brought to it, and (c) whether the pack animals can forage or drink water along the way.
The pack animals consume some supplies on the way, so getting the same amount of supplies a greater distance takes exponentially more pack animals, until you reach a “limit” where all supplies are consumed along the way. The more water the pack animals have to carry, the further distance they can travel.
This leads to the maximum supply distances used in D@W. It turns out that when you factor in the pack animals and build a spreadsheet you get these results:
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In terrain where pack animals can forage and drink freely, at a supply distance of 14 days, 17 more pack animals are required, and the total gp cost is 3.40gp per day per 50 men.
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In terrain where pack animals can drink, but not forage, at a supply distance of 6 days, 8 more pack animals are required, and the total gp cost is 3.35gp per day per 50 men.
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In terrain where pack animals can neither drink nor forage, at a supply distnace of 1 day, 3 more pack animals are required, and the total gp cost is 3.56gp per day per 50 men.
I averaged these to 3.50gp per day per 50 men. That in turn leads to (120/50 x 3.50 x 7 ) 58.8gp, rounded to 60gp.
Since few people want to worry about the exact number of mules in the supply chain, this all gets handled behind the scenes. The player just needs to know the number of units and it’s assumed low level adjutants and quartermasters ensure the right number of pack animals are assigned so long as the gold is spent.
Scribes & Supply Lines, the hot new game from Alex Macris.
Coming Fall 2013!
OT: This was great to see. I had assumed there were formulas behind those supply numbers, and now I can tweak to my heart’s content when supply is scarce - for example, if my players want to take their armies north to end those Ice Elf raids once and for all.
The one thing that bugs me about the 120 man units is the fact that (iirc) manual of arms lets you train 50 soldiers at a time. I think it would be helpful if you could bump manual of arms to 60 at a time to match. training a unit half at a time or all at once for cavalry, just fits better.