Where/how are number of recruitable mercs determined?

[bitparity]

Are they tied to manpower, do they follow regular max_manpower modifiers or anything? I ask because I'm reducing country manpower, but I"m not entirely sure this is reflected in the mercenaries, which means an over-reliance on them (though that is curiously historically accurate...)

 

[Wizzington]

It's tied to foreign neighbour provinces. If you hover over the mercenary amount you can see how many mercenary regiments are arriving each year and from where. Mercenary regiments will not appear in provinces that only border your own provinces.

 

[bitparity]

Is it tied to the manpower of foreign neighbor provinces? What define/modifier should I be looking for to mod it.

 

[Cheexsta]

It's tied to the population, not manpower, of neighbouring foreign provinces. I think in defines.txt, the line _CDEF_MERCS_MONTHLY_CHANGE_ refers to how many mercs per foreign population are generated. Try tinkering with that number and see what happens.