If you should set up an army of 10 units in the game, what would it be.
The problem usually is set a little bit different. Imagine WW1. Assume you have 1 mio soldiers and you should equip and field them to protect your country.
One of the objectives of Infantry is to block enemy movement so enemy forces cannot invade your country or destroy your artillery. You need replacement troops for your infantry. Infantry can capture cities and control area.
Cavalry was used to scout / recon and charge at supply, artillery.
Artillery was supporting infantry in attack and defence and was weakening enemy troops from distance.
- An infantry soldier was equipped with a rifle, 100 shots (ca. 5 kg) and some hand grenades.
(Every 10th or 100th infantry man may had a MG and maybe 1000 shots.)
- A cavalry soldier had a horse, a rifle, a sabre, 100 shots. (As far as I know Cavalry needed about 4 times as much supply compared to plain infantry due to supply for the horses.)
- An howitzer took about 12-25 soldiers for operation, Field artillery team, logistics. A couple of horses for moving the howitzer. Depending on kaliber a grenade may weight between 5 - 20 kg. (Siege artillery shells were heavier and could have a weight between 100 - 1000 kg).
A rifle weighs about 5 kg and costs maybe 100 $. 100 shots are estimated with 5 kg.
A howitzer weighs 1.000 (light) - 8.000 (heavy, siege) kg. 100 shells are about 800 - 1.500 kg. So a howitzer has estimated industrial costs equivalent to 200 - 300 infantry soldiers.
A siege weapon like "Dicke Berta" had a cost of 1 mio Mark, a life expectancy of 2.000 shots and each shot (ca. 1.000 kg) cost 1.000 Mark.
According to literature, artillery bombardment caused about 62% of military casualties in WW1. Average ammunition costs to wound or kill a soldier were about 35.000 Mark!
Every front soldier in the trenches had to be supported by 6 - 8 civilian workers at the homefront (war industry and supplying industry etc.).
In scenario A I would pick something like:
6 Artillery, 3 Riflemen and a Cavalry.
Transferred to the 1 mio soldiers scenario this are
- 300.000 infantry men (= 20-30 divisions)
- 100.000 cavalry men (= 10 divisions)
- 600.000 artillerists = 18.000 - 30.000 howitzer (3-6.000 batteries)
On a 300 km front-line this would be an infantry division per 10 km backed up with a howitzer every 10 m.
One limiting factor is the supply with artillery ammunition. Since a howitzer can fire multiple rounds per min, usually a few howitzers are enough to spend the daily ration of shells. Huge military operations in WW1/2 required months of stockpiling ammo for a heavy artillery bombardement. German production of Gun Powder per month in 1917 was 14.000 t. If you assume a production of 30.000 t ammunition per month (?), the 30.000 howitzers could fire the complete monthly production in just 1 hour.
The 1:3:6-ratio sure is possible but it is probably a very expensive ratio regarding costs for equipment, operation and supply.
Problem with Civ5 is : unlimited ammo, unrealistic military costs, no supply system.