The land maintenance cost is a country's monthly expenditure required to maintain its land military forces. Each man in every land unit requires a small amount of money for maintenance. You can see the land support cost on the land military information screen, labelled "Monthly Maintenance Cost".
As a rule of thumb, the yearly maintenance cost for a unit, assuming you are using 50% maintenance and are not above your support limits, will be roughly one-twentieth of its recruitment cost.
Payment of Maintenance Costs
Maintenance costs (naval and land) have the highest priority. Typically each cost is deducted from a country's treasury at the start of each month, but if the treasury is empty then it is deducted from the monthly income. This deduction to income happens before income is channeled via the budget, thus it is inflation-free. However, it also means that the amount of economic resources (see below) is reduced.
If a country has no money in its treasury, and it does not have enough monthly income to pay maintenance, then it will be forced to take a loan. If it cannot take a loan, it will be forced into bankruptcy.
Land Maintenance Level
The land maintenance level is a percentage, from 50% to 100%, of the "full" cost of maintenance that a country may choose to spend. At 50% maintenance, maintenance costs are half as much as at 100% maintenance. There is no penalty for less than 100% maintenance except for lowered morale of all land forces. (Because the morale penalty is not that great, good players use 50% maintenance most or all of the time; this is why "full" is scare-quoted above.)
The land maintenance level is set by the Maintenance Level slider on the land military information screen.
Land Support Limit
The land support limit is the maximum number of men under arms that a country can have without incurring dramatically increased maintenance costs. The limit may be exceeded, but at a dramatic surcharge to the monthly maintenance cost.
You can see the land support limit on the land military information screen; it's the number labelled "Supportable Amount".
The land support limit is computed as follows. Every country starts with 5000 as its base land support limit. To the base is added:
- 1000 per quantity of surplus monthly income called "economical resources"; DP slider toward Land increases this for land units. It is 3000 support per 10d monthly at Land 10 and is 1000 support per 10d at Land 0. Surplus income is the income after paying maintenance and interest.
- 10000 per conscription center
- 5000 per weapons manufactory
- 1000 times maximum manpower
- 2000 for each 100 units of grain produced
- 1000 for each 100 units of grain traded
You can see the breakdown of the factors above on the land military information screen, by mousing over the "Supportable Amount" readout to get the tooltip.
To see your country's grain production and trade, select a grain province and click on the grain icon. This displays information about grain in the mini window, including "units of grain" which your country produces and trades.
The support from economical resources depends on the Naval/Land domestic policy slider. The further toward Land the slider is, the less income is required for each 1K support. That is, the "economical resources" contribution to support goes up substantially with each click toward Land. (Further toward Naval, there is more support for ships. You can see the Naval FAQ for more details.)
Economical resources are only gained based on the amount of monthly income actually going to tech research and/or treasury. Looting counts -- economical resources will be higher in months of looting. However, income spent on interest and military maintenance is not figured into the economical resources support. Thus it is possible to spiral down on support, because if support drops below the number of troops in play, then more income is going to be spent on maintenance, and support is going to drop further because economical resources will drop.
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The naval support limit is the maximum number of ships that a country can have without incurring dramatically increased maintenance costs. The limit may be exceeded, but at a dramatic surcharge to the monthly maintenance cost.
You can see the naval support limit on the naval military information screen; it's the number labelled "Supportable Amount".
The naval support limit is computed by summing up the support received from the following factors:
- Ports. Multiply the BTV for every province that has a port with 4, and then sum these values.
- Shipyards. Add 10 for each shipyard you own
- Merchants. Multiply the yearly number of merchants you receive with 10. Then truncate this value to nearest tenth of an integer. Note that 1) the tooltip will show the value before truncation and 2) often the value is calculated as (# yearly merchants - 0.1) * 10.
- Naval manufactories. 5 for each naval equipment manufactory
- Naval supplies produced and traded. 1 for each 100 units of naval supplies produced or traded.
- Economical resources. DP slider toward Naval increases the support limit: monthly income divided by 4 at fully Naval or divided by 20 at fully Land. The value is truncated to nearest integer.
Computation of Land Maintenance Cost
Under the Limit
When a country is below its land support limit, computation of its maintenance cost is fairly simple. At 100% maintenance, the maintenance cost for one army unit of a type is the base cost of the unit type divided by 120, multiplied by inflation. The land maintenance cost is just the sum of the three individual unit types' support costs times the number of army units of that type.
Let's formalize the paragraph above. For each unit type:
support_cost_per_unit(type) = base_cost(type) * inflation * maintenance% / 120
The support cost per type (which is shown on the army screen), is just the number of units of that type, times the support cost per unit:
support_cost(type) = #units(type) * support_cost_per_unit(type)
The land support cost is the sum of the three support costs:
land_support_cost = #infantry/1000 * support_cost_per_unit(infantry) + #cavalry/1000 * support_cost_per_unit(cavalry) + #artillery/10 * support_cost_per_unit(artillery)
We can factor out inflation, maintenance%, and 1/120000 to get the following:
land_support_cost = inflation * maintenance% / 120000 * (#infantry * base_cost(infantry) + #cavalry * base_cost(cavalry) + 100 * #artillery * base_cost(artillery))
Over the Limit
When a country has exceeded its land support limit, the land maintenance cost is raised considerably. In fact it rises with a square law. To compute this amount, we need to first compute the number of troops (as weighted for unit size), and the amount over the limit:
#troops = #infantry + #cavalry + #artillery * 100 #troops_over_limit = #troops - land_support_limit
Now the penalty, per type:
penalty(type) = 5 * support_cost(type) * #troops_over_limit / #troops
Now we can revise the support cost per type of unit, as:
support_cost'(type) = support_cost(type) + penalty(type)