Just How Big is your Army?

 As modern people we have trouble thinking like medieval people. Whether it is about family size, how far is 'far', or other things, we think differently.

  Of course.

  Another thing we often get wrong is army size. We think of the vast, often conscripted armies of the Napoleonic era forward and assume 'army' = 'huge numbers'. Hollywood doesn't help! But how big was a medieval army? And why do RPG players care?

  Well, we care because it gives us an idea of what we can make our campaigns look like.

  

 Before we talk about armies we have to decide - what kind of army are we talking about?

  See, every nation tends to have two armies; a standing army and a war time army. The standing army is what is always there, the wartime is the maximum force you can bring to bear in an all-out war. Since you might not have your campaign in constant all-out war, let's start with a standing army.
  

  I can't remember which historian said it, but one said that in the early medieval period the 'standing army' and the 'government' were largely the same people; knights, barons, etc. ruled and fought or, more to the point, ruled because they fought. Indeed, the medieval three types of people were those who worked, those who prayed, and those who fought. These men and their retainers are the main force of any medieval kingdom.
  Historically the cornerstone of the feudal system was the fee (root of the term 'fief') defined as, roughly, 'the amount of land, peasants, etc. required to support themselves and provide at least enough excess to feed, equip, and support a knight and his personal retainers'. The most historically accurate way to figure out how large a standing army would probably be to figure out how much of the kingdom's area is settled land, divide it by the average size of a knight's fee, figure out a rough percentage of the which is already enfeoffed, and do the math.
  The trouble is historians have effectively thrown up their hands and declared no one will ever know the average size of a fee because there wasn't one. The variables are too high and the documentation too scattered and partial.
  Besides, its just a game, right?
  So, instead, let's look at the DMG and PHB.
  The average area of the holding of a high-level fighter is between 3,500 and 4,000 square miles (yes, really) or, well, Lebanon. Or 5 times the size of the Duchy of Saxe-Coburg-Gotha. I am assuming that the vast size of a 9th level fighter's holding is based on one simple fact - it is a wilderness holding and the character is much higher in rank than mere 'knight'. If the fiefdom was well inside a settled area we would need to assume it was much smaller.

  [note: the smallest fighter fiefdom, 314 sq. mi., is as big as Kiribati and the largest, 7,850 sq. mi., is as big as Israel. At this point my sons point out 'Well, sure; King David was at least 9th level'].

  So here are a ton of assumptions - a 9th level fighter has huge tracts of land but few citizens at first. He is beholden to another lord but has the space to give fiefdoms to several knights (and barons!), eventually - that makes him a duke. Thus, the followers of a fighter are about the same as the followers for a duke. Dukes each have their own vassals that have, aggregate, about the same number of troops as the duke. The king is, really, another duke so he gets more of the same. A Lord or Free City would be, oh, half that.
  Therefore, to determine the size of the standing army in a campaign kingdom do this:

  [(N+1)x2]+H = X

  where N = the number of duchies (or equivalents) in the kingdom, H is the number of lesser nobles, and X is the number of times you roll for followers and leaders in the DMG.
  If we do this for my campaign it looks like this:
  There are 2 duchies/equivalents, 2 lordships/equivalents, and the king, so the formula would be:

[(2+1)x2]+2= X, or 8 rolls for followers and leaders.

  Throwing some dice gives me a total of about 680 troops, 400 of which are heavy infantry, 4 5th level leaders, 3 6th level leaders, 1 7th level leader, and a 3rd level lieutenant.

  "OK, Rick, even if I accept all your wild guesses who are these troops and what do they do?"

  These are garrison troops, the guys who man the castles, towers, custom stations, border forts, etc. The king's guards, maybe even the marines on royal warships could come from these troops as well. Some of them are going to be mercenaries who are paid via the taxes collected, the rest will be professional soldiers paid via the same manner. So we can estimate that Seaward's standing army is 650 to 700 troops.
  These aren't city guards, though, because city guards don't typically leave the city while armies do! Besides, troops and guards would have very different armor, weapons, and training. These forces also don't come from the NPCs that are otherwise also part of the population.

  Now, in time of war the standing army is joined by levies. These troops are drawn from free men (peasants, yeomen, townmen, etc.) and are usually of lower quality in training and equipment than standing forces, but not always. In Real Life some area, especially Free Cities, had top-quality militias so their levies were solid, well-trained and excellently equipped troops!
  Rather than do a ton of math myself I want to point to this work by John Savage because he does the math for me.
  Bottom line - your levies will never be more than 7% of total population unless you want starvation for the next 1-3 years and even then that assumes near 100% turnout. Further, only about 1.5% - 2% of the population can be massed into an effective fighting unit at a given time and place. Applied to Seaward, this means in a 'real war' the kingdom could probably field about 10,000 levied troops BUT other levies would also free up the standing army so that they, too, could take to the field of battle. 700 is relatively small compared to 10,000 but the presence of professional soldiers with better gear and higher morale as well as the tough, experienced, and leveled leaders would make the levy troops much more effective in combat.

  We also need to talk about nobles. I forget who the writer was, but someone once said,

   'The "leaders of the army" and the "government" were the same people. Indeed, the government was in charge because they led the armies'.

  Remember the formula, above? Dukes, lords, even the king, are all either themselves skilled (probably leveled) fighters and such or such men exist as knights to fight for them. Traditionally each noble had 4-9 other cavalry with them in battle to fight in groups called 'conrois'; while a particular conroi might be all noblemen it wasn't uncommon to have common-born men who were well-trained cavalry accompany knights as personal assistants and to add to a conroi's strength. These commoners who were heavy cavalry had a fair amount of authority over non-noble troops and were often in charge of them.
   They were called 'sergeants'.
  Conrois also typically included a few squires and servants and their own focused supply train.
  Remember the formula I posted above? X also equals the number of conrois that can be called up to fight. In the case of Seaward, that is a total of 50 top-notch heavy cavalry with its own support and logistics. Again, 50 isn't much compared to 10,000 but the morale boost of leadership is large and the damage even a small number of noble cavalry can do to enemy formations should never be underestimated.

  There it is, a ton of assumptions which you can feel free to tinker with, blow off, etc. But it is also a set of guidelines to help you figure out how big your campaign army can be.