Army Sizes

I became interested in the relationship between army size and population and did a quick survey - sadly I found it quite hard to get 18th century data on the Web, but Napoleonic data was ready to hand, so here is a comparison between the major states and some small states I looked at for comparison.

 

As you can see, major states were running at about 1 - 1.5% pre the Wars. Austria and Russia both increased army sizes in the region of c 1/2  - 2/3rds at peak. France had to find a lot of men to fight all the others, so is running at 2-3x the other big players. Britain is a bit misleading owing to the size of its Navy (not considered), and Prussia has a small population even in Napoleonic times. I recall reading once that if the population in arms of a country goes above c 5% it really suffers economically (if you consider that all the soldiers are fit and active males, who are about 1/6th of the population, then 5% of a population is pretty much 1/3rd of all active males in a country) so France and Prussia after the wars must have been pretty unpleasant.  

I also did some analysis of smaller states, as you can see they - on average - at their height are less militarised than the major powers. I counted the men in the units and multiplied by 1.5 for the "tail". Westphalia is possibly too high, I assumed 3 battalions per regiment for all their regiments but it may not have been uniform, and one cavalry regiment was paid for by Wurttemburg. Also, both of these states were ruled by Bonaparte family members so may have bean "leaned on" more than the others to provide men and material more in keeping with French style ratios.

As to why the small nations have a smaller % in arms, I don't know.

To estimate sizes in the18th century, I assume they are similar to pre-Napoleonic mass army times, then if we assume "Height Of" numbers for the smaller states had about the same increase as for Russia and Austria in the period, then a "Normal Situation " is c .75 - 1.5%, which the bits of 1801 data I have seems to agree with.

(Clarification from the comments below - I think the "peacetime" army is about 1% safely, but a fully mobilised manpower of 2% (trainees, reservists etc) is probably an achievable level that is "safe" economically without putting a country on a war footing.

So as a rule of thumb, your Imagi-Nation should be running at about 1% of  population for the army, unless you are totally militarised like a tinpot Prussia. Incidentally, the ratio of  Horse to Foot of the small countries I looked at is about  0.3 : 1 Horse:Foot, so about a quarter are cavalry.

For what its worth  European Turkey is c 8m souls at this time, so to field a peacetime army of about 20,000 (what I had initially designed x 1.5, as above) my Imagi-Nation (New Byzantium) needs to appropriate about 2m people - or 1/4 of it. That seems unrealistic, 1/10th was more what I was thinking, so clearly I need a lot of mercenaries (check) and a major trading city seaport to afford them!