Worlds of Design: How Big is Your Army?

For those who prefer "realistic" numbers in RPGs: Inflated numbers of combatants for battles litter history books, derived from wildly inaccurate contemporary histories. We can do much better in figuring out actual numbers.


Picture courtesy of Pixabay.

Some GMs don't care about practical limitations, and will happily claim an army is hundreds of thousands strong. But that kind of nonsense will put off some players, breaking their immersion in the setting, destroying their suspension of disbelief - because it's nonsense, barring extraordinary magic or combatants who don't need to eat!

As player characters progress to greater capabilities, some may become involved in warfare. I'm discussing this for the benefit of those GMs and game designers who want their world to make sense. Keeping the numbers down may also help when you're trying to fight out a battle on the tabletop in a campaign.

Army Inflation​

Many decades ago, I recall being in awe as I read about one of three Battles of Panipat (India) involving 600,000 men according to accounts of the time. The numbers were repeated in a 20th century dictionary of battles, yet sounded immensely inflated. They were, as are the claims from ancient and medieval times for many other battles. Logistics (supply, more or less) limits the size of pre-"modern" armies. In order to feed them and their horses, you can only concentrate so many in one place (not counting cities that have developed long complex supply chains, though few cities exceeded the size of armies in pre-modern times). Modern estimates for any of the three Battles of Panipat are for less than 150,000 total combatants in the 18th century battle, less than 100,000 for each of the older battles, not 600,000.

I find that counting, or relying on someone else to count, helps solve many questions; but even the commanders of pre-modern armies didn't know how many troops they had. So we resort to other methods.

Let's take some examples of battle sizes.

The Battle of Hastings and Marathon​

In the late 19th century, estimates for the size of armies at the Battle of Hastings (Norman conquest of England) were around 25,000 each. Today as we understand circumstances better, estimates are typically 6,000-8,000 per side. Not a big battle, but huge in its results.

Numbers cited for the Battle of Marathon (490 BCE) by the ancients are wildly unreliable. A method used by modern historians to try to achieve a reasonable range, was to compare the size of the (excavated) Persian camp to the size of other camps where numbers are fairly well known (as in the past few centuries, or some Roman camps). The Persian camp couldn't possibly accommodate anything like the numbers cited.

Another way to estimate number of participants is to know the number of men manning a ship. Greek and Persian triremes were quite standardized, and we know their size from excavating sheds where triremes were stored. If we know that the complement was typically 200 men, we can calculate that 371 ships (reported in detail by Herodotus for the Battle of Salamis) equals 74,200 Greeks. A similar logic can be applied to Viking armies, but here many historians distrust the number of ships reported by contemporaries, so we end up with estimates varying from hundreds to thousands.

Yet I still see wildly inflated numbers from works of the time repeated in modern day historical books.

Barbarian Invasions​

How about numbers of "barbarians" in ages of invasion? We have almost no reliable numbers. One that is reliable is the number of Vandals (with some Alans) crossing from Iberia to Africa, because the Romans (who transported the Vandals to participate in a civil war in Africa) had to know how many ships they needed. I've seen 80,000 quoted by historians, including women and children. Which likely meant no more than 20,000-25,000 warriors.

The Battle of Towton​

What may have been the bloodiest battle ever fought on English soil, the Battle of Towton (1461), involved 50,000-65,000 men counting both sides - about 1-2% of the population of England at that time!

Modern Battles​

Even in Napoleonic times, when roads were much improved and the supply system was designed to cope with large armies and rapid movement, the concentration of more than 100,000 on a side was quite rare, and confined to later in the war (Borodino, Leipzig for example)

The bloodiest battle of the American Civil War (Gettysburg) involved less than 100,000 on either side. The largest number of one side in any battle was Chancellorsville (133,000 Union). These were three and four days battles, not a single day, in times when railroads made supply immensely easier.

Contrast this with notions/claims of many hundreds of thousands in much more primitive circumstances. Such high numbers simply aren't possible, nor was there any way for contemporaries to know actual numbers.

Armies in Your Campaign​

When you run an RPG campaign involving warfare, you don’t generally need to get into details of latrines, camp followers, and pay, but you might want to recognize the difficulties involved in moving and maintaining very large numbers of troops. Most warfare in the melee age was “small war” that involved hundreds rather than thousands, and rarely tens of thousands let alone hundreds of thousands.

I used to live in “Battle Creek” Michigan. That eponymous “battle” involved all of . . . three men (no deaths). A castle could be held by less than a hundred men, unless the attackers were highly motivated and very numerous.

My advice is, forget the vast numbers and focus on interesting interactions.

Your Turn: What are the most numerous armies that have ever actually fought out a battle on the tabletop in your campaign?
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Lewis Pulsipher

Lewis Pulsipher

Dragon, White Dwarf, Fiend Folio


I've been working on a Starfinder setting, intended for publication, called the Kronusverse and Colonial Space. Earth (Kronus) is the old human homeworld, currently estranged by an awakened Earth that exiled humanity for it's depredations. The nearest 13 star systems to Earth were resettled by humanity called Corporate Space, under control of the MegaCorps. 50 years later the underclasses unhappy with Corporate rule, through crowd funding, religious funding and commercial funding a movement to escape Corporate Space ensued building colony ships to the wilder regions beyond. Over a century 36 star systems surrounding Corporate Space was settled in a region known as Colonial Space. Once all independent colonies intermixed with alien occupied worlds, but following an incursion by an overwhelming militant alien species forced the independent colonies to unite their militaries and resources to defeat this enemy. After 7 years an armistace was achieved. Following that the colonies joined to fom the Confederation of Independent Colonies of Colonial Space (CICCS). The total population of the entire Confederacy number over 6 trillion citizens. The military capital world colony alone has a population of 1.4 trillion, most colonies are in the tens of millions.

The Colonial Navy and Colonial Marines form the permanent military of the Confederation. The two most populated colonies host the Colonial Navy inextensive orbiting shipyards. Five full fleets patrol the widely dispersed region of the colonies. (You'll notice that the Colony's chief naval architect had an affinity with sealife). The Colonial Marines consist of recruits from across the colonies of many races, but generally not from most civilized worlds. While units are measured in divisions, regiments, brigades, battallions, companies, platoons and squads, the last one is most like an adventuring party, up to 6 soldiers. So while I have Marine drop shops from company size down to squad size exist, even though the latter isn't compatible in modern warfare - squads are generally too small for a small unit. I've designed these Colonial Marines to focus on squad tactics for many operations - better fitting the game table of players.


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Some spellcasters have "Augury". If cast before almost any WW I style battle, the attackers would have been told that attacking would bring them "woe". Their King might not listen the first time, but likely would the second....
It'd be interesting certainly to see how that'd work with symmetrical spellcasting. I imagine it'd be similarly effective to pregame prayers for sporting events.


B/X Known World
Again - source, please.
Let's turn this around a bit. So for those who are not as knowledgeable about these things, what are some good sources you'd suggest for people to educate themselves on these things? A few writers I'm familiar with are John Keegan, Max Hastings, and Martin Gilbert. Though they generally focus on more modern warfare. Any recommendations about ancient or medieval warfare? Perhaps even pike and shot? I mean beyond a heap of Osprey books.


The spell Sending would be my first pick to help warfare management.

Effective communication would be far more effective than anything below 9th level spells, which would be devastating by design. From the fertile crescent of Babalon to present day Ukraine, effective communication has been at least as important as weapons or numbers. I'd expect a caster to focus on communication and reconnaissance with just a few blasting spells or conjurations in the actual battle at key moments. Even just being able to Dimension Door the king out of danger in a route would be huge.

Let's turn this around a bit. So for those who are not as knowledgeable about these things, what are some good sources you'd suggest for people to educate themselves on these things? A few writers I'm familiar with are John Keegan, Max Hastings, and Martin Gilbert. Though they generally focus on more modern warfare. Any recommendations about ancient or medieval warfare? Perhaps even pike and shot? I mean beyond a heap of Osprey books.

For people who want academic sources but not academic treatises, check out Ancient Warfare Magazine and their corresponding podcast.



Effective communication would be far more effective than anything below 9th level spells.

Let's start at the bottom with cantrips.

Communication is a force multiplier.

Message (cantrip)
120ft range, doesn't require line of sight, cannot be heard by anyone else. Caster can be close-ish without being next to commander. Have the 1st level caster act as a relay to runners and touching base with the commander every round or two. Depending on formation, the message-caster could coordinate 2-4 units that are up to 240ft apart. Very valuable for stealth/night operations or where you have trenches or battle lines.

Speaking of trenches, another mutiplier is engineering & logistics.

Mold Earth (cantrip)
It moves 125cf of dirt 5ft every 6s. That is ~10,000lbs/5T/4500kg. A wizard drop-out can dig 600ft/182m of trench & berm each hour or more than a mile of trench each day.

By the same token, if they get within 30ft of a wall built on anything but bedrock, they can collapse it/make a breaching ramp.

If you assemble a trebuchet, you can have up to 5T of dirt move around to help reload.

Shape Water (cantrip)
A logistical boon as it can control 125cf/8000lb/1000gal/3785l of water. Make it take a simple shape, move to a wagon, get in the wagon, then freeze solid for an hour. Each cantrip-weilder can have two of those at a time.
They can act as pumps either to supply your troops or to drain the ground water faster than it can recharge so your enemy's wells go dry.

Control Flame (cantrip)
Only useful at short ranges offensively, defensively it is fantastic. Fire is in the trinity of Loot/Pillage/Burn so being able to completely extinguish a fire while it is small-ish is critical. And to be honest, a 25sf fire is not really small.

Most cantrips offensively are little more effective than a (fire) arrow so not really army-impacting.

Moving up to leveled spells, let's focus on the rituals as they are slow at-will spells.

Leomund's Tiny Hut (3rd) is the ultimate command post for a general. Temperature controlled, you can see out but others can't see in, and protects you from spells up to and including meteors.


Animal messenger (2nd)
Upgraded messenger pigeons who can go to any location you have been before. Oddly slow, traveling only 2mph.

Skywrite (2nd)
Tell the whole army commands. Mock your enemy.

Phantom Steed (3rd)
A very fast horse for messengers. Doesn't require food.

Water breathing (3rd) - affects 10 people for 24 hours. Put scouts and messengers in rivers and creeks moving invisibly in broad daylight. Or sabatours. Or assasins.


B/X Known World
Find Familiar. Perfect for recon, scouts, and patrols. Even with the limited range, getting a bird’s-eye view is a great advantage. Distance to the horizon at ground level is limited to about 3 miles. If you’re 100ft up, it increases to 12.3 miles.

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