Could the Persian Empire logistically support an army several million strong?

[Justin Swanton]

Picking up from a diversion on the Killing and Being Killed thread. The debate about the real sizes of Achaemenid armies has lasted almost as long as the Achaemenid Empire itself. It would be interesting however to examine the practical challenges in gathering, moving and supplying an army of several million men using the infrastructure and technology of the time. A few problems that immediately come to mind are:

1. How to grow and store enough food to feed such an army for the campaigning season? 2. How to transport that food to where the army will need it? 3. Where does the manpower for such an army come from? This explores the population size of the Achaemenid Empire and whether so many men could be absent from their homes for an extended period of time. 4. How does this army move from one place to the next? This covers problems of length of the column, size of encampments, etc. 5. How would such an army deploy for battle? Obviously in great depth, which poses the question: why such huge numbers if most won't actually fight? Intimidation by warcry? I'm minded of Issus.

My own off-the-cuff take:

1. Growing food for 3 - 4 years should do the trick. The biblical account of Egypt storing food during seven years of plenty to be distributed during seven years of famine is IMHO founded on something factual: if nothing else the practical possibility of keeping grain from spoiling for several years. I suspect putting it in large rooms then sealing the rooms completely would work. Remember the grain found in Egyptian tombs after thousands of years? It was still edible.

2. Ships to a large extent, and overland to a limited extent. Thus the contingents of the army come together only at the coast where huge ship-supplied grain silos are ready for it.

3. the Achaemenid Empire had about 50 million people. That's about 25 million men of whom about 1/3 to 1/2 were of military age, which give you about 8 million men from which to draw an army. No problem. Most of the men stay at home and keep things going.

4. Obviously not by conventional road or track (I believe this is the principle argument against huge Achaemenid armies). Question then is whether there is any historical evidence for the preparation of broad avenues along which the army, dozens of men wide, could march in a huge, loose crowdy column. Or at least no evidence against the theory.

5. I remember that quote from Napoleon: "Two armies are two bodies of men who meet and try to frighten each other." The morale element of a battle is paramount - sapping your enemy's will to fight. It's a bit like an elephant flapping his ears to make himself look even bigger. Bringing a huge army to the battlefield was the classic way of intimidating one's opponent to run before even making an attempt at battle. So the great majority of an Achaemenid army wasn't supposed to fight, just look scary from sheer size.

And now to the floor.

[RichT]

Just to note that as for 'othismos', this is a well trodden floor, and it might be worth collecting, linking to and reading existing long threads like this one:

http://soa.org.uk/sm/index.php?topic=1745.0

and posting only if you have something new to say, or some new evidence or argument to advance.

[Patrick Waterson]

A few thoughts to start with.

The men mobilised for such a campaign are part of the general population which normally by and large feeds itself.  The challenge for feeding them when they go on campaign is primarily about moving sufficient food close enough to where they will be campaigning before they start and then keeping the distribution going while the campaign lasts.

We are therefore looking at a transportation of surplus exercise, a storage situation and access facilities for loading and unloading sufficient quantities of material on an ongoing basis.  I think Justin has civered the basics of storage.

Central to the whole arrangement is transport and the organisation of transport.

To provide 1.7 million (or rather 3.4 million if noncombatants are provided for) men with a daily choenix (roughly 2 lbs) of food each, which Herodotus considers the minimum requirement, requires moving about 6.8 million pounds or about 3,000 tons per day.  This translates to unloading about sixty 50-ton ships on a daily basis, a figure well within the capacity of the coastal cities of the Persian Empire to provide and the average Greek beach to handle.  At the other end of the pipeline, loading sixty 50-tonners daily should not tax the capability of a decent port.

So, as long as there are no storms and no hostile fleets interfering with the system, there should be no problem keeping Xerxes' army supplied.

Why mobilise so many when really only a fraction (essentially the 300,000 subsequently chosen by Mardonius) could be considered effective?  There are a number of considerations here.  One is that when the cat is away, the mice will play, so it helps to bring the mice along with you.  Another, as Justin mentions, is sheer intimidation: the Ionian Revolt of 496 BC collapsed because many contingents simply drifted away when they learned of the size of the Persian army coming against them (a much smaller army than Xerxes deployed).  The defenders of Thermopylae were seized with fear at the report of the size of Xerxes' army (Herodotus VII.207).  Size mattered, and in some cases did the Persians' work for them.  Then there was prestige: the larger the army, the greater the ruler's prestige, and prestige was what held a ruler's empire together, or at least kept the ruler in place at the top.  It is noteworthy how when Xerxes' prestige crumbled, he became an assassination target.  Prestige mattered.

[Erpingham]

We are of course already repeating our earlier arguments

Just on the basic numbers.  We can agree that 1kg of wheat would probably work as a minimum ration for a while.  It would give about 3500 calories a day, on which we could assume the troops would survive as long as they are marching and not expecting to fight.  This actually gives nearer to 70 ships if we take Patrick's figures.  One question we might ask is how long is the supply cycle - load, sail, unload, sail back?  This would give us some idea of the ships needed.

We should note that patrick's figures assume no horses or other animals in the army needing feeding.  A horse needs about 1.7- 2.00% of its body weight in dry feed, according to the internet.  Grazing possibilities should be assumed minimal.

Experts in geography can look at how much impact a need to move between suitable beaches would have on march rates.  Other march rate questions would be the length of time taken for unloading, distribution, food preparation and watering each day.  Obviously, the shorter the marches, the more supply would be required in total.  The longer the campaign, the more effect sub-optimal diet will have on the capabilities of men and horses.  Horses are very difficult to keep in condition on campaign.  We should note too the length of the army, the effect of perhaps multiple supply points and fouling of water supplies.

And all that without even considering comparisons with other ancient armies or other eras.

[Mark G]

Entirely without irony, let us not forget the sheer volume of shit produced by this size of force.

And move on to just re reading old posts and agreeing that no one has anything new to say on it and no one is likely to either because no one who takes it seriously has changed their mind since last time since no new research will be acceptable to one position whilst no new period sources have been discovered to challenge the other position.

[Justin Swanton]

It might be an idea to approach the subject from the angle of probability, i.e. we have the primary sources which all give the Persians huge numbers. Question then is to see if there is any insuperable obstacle to the Empire raising, supplying and moving armies of this size. If there are no insuperable obstacles then the burden of proof is on the other side: the sources can be assumed to be substantially correct unless proven otherwise.

[Imperial Dave]

Entirely without irony, let us not forget the sheer volume of shit produced by this size of force.

And move on to just re reading old posts and agreeing that no one has anything new to say on it and no one is likely to either because no one who takes it seriously has changed their mind since last time since no new research will be acceptable to one position whilst no new period sources have been discovered to challenge the other position.

[Erpingham]

It might be an idea to approach the subject from the angle of probability, i.e. we have the primary sources which all give the Persians huge numbers. Question then is to see if there is any insuperable obstacle to the Empire raising, supplying and moving armies of this size. If there are no insuperable obstacles then the burden of proof is on the other side: the sources can be assumed to be substantially correct unless proven otherwise.

Anything that is not impossible could happen.  What happens most of the time is a tiny subset of this.  It is best for those arguing for the outlier to make a case why, on this occassion, the nearly impossible is in fact the most likely case. 

[Justin Swanton]

Entirely without irony, let us not forget the sheer volume of shit produced by this size of force.

If it can be proven that the entire army had to march along a single track or narrow road then we can automatically rule out several million men right away (the column would be ridiculously long). But if it marches along several wide, roughly-cleared avenues then poo is not a primary consideration. The avenues would hardly be roads - just passable ground. The voortrekkers went into the African hinterland in waggons and didn't use roads.

And move on to just re reading old posts and agreeing that no one has anything new to say on it and no one is likely to either because no one who takes it seriously has changed their mind since last time since no new research will be acceptable to one position whilst no new period sources have been discovered to challenge the other position.

My take is to believe the primary sources if:

a) they agree or at least don't irreconcilably contradict each other
b) they accord with data from other sources like archaeology or at least are not contradicted by it
b) what they maintain is possible

My take on academics is a bit different. I will read and pay attention to them, but they live several thousand years after the events, in a world dramatically different from the period in question, and are not by training generals, economists, horsemen, merchants, seamen or waggoneers. They can't actually affirm what is or isn't possible* in these disciplines simply on their academic experience. I much prefer making sense of the primary sources (written by people much nearer the time in question and who often had some experience of at least one of these disciplines) than discounting them en bloc.

* I'm impressed by the way Christopher Matthew rules out holding a sarissa overarm a priori simply by affirming it's too heavy. How did Renaissance pikemen manage?

[Justin Swanton]

It might be an idea to approach the subject from the angle of probability, i.e. we have the primary sources which all give the Persians huge numbers. Question then is to see if there is any insuperable obstacle to the Empire raising, supplying and moving armies of this size. If there are no insuperable obstacles then the burden of proof is on the other side: the sources can be assumed to be substantially correct unless proven otherwise.

Anything that is not impossible could happen.  What happens most of the time is a tiny subset of this.  It is best for those arguing for the outlier to make a case why, on this occassion, the nearly impossible is in fact the most likely case.

Nearly impossible?

[Erpingham]

If it can be proven that the entire army had to march along a single track or narrow road then we can automatically rule out several million men right away (the column would be ridiculously long). But if it marches along several wide, roughly-cleared avenues then poo is not a primary consideration.

Patrick's theory assumes that the whole army is next to the coast on a daily basis.  Doesn't this preclude "numerous roughly cleared avenues"?  Also, how long would each of the sub-columns be?  There is a paper on 17th century armies which concludes that an army of 60,000 men and its baggage would stretch 198km in single file.  I think it would need to be something like 15 wide for the  front to be reaching the new camp as the back left the old one.  You are talking of an army 60 times this size.  Ok, not entirely compatable - the persians are carrying much less food with them because they are resupplying daily - but it does provide a sense of proportion.

[Duncan Head]

If it can be proven that the entire army had to march along a single track or narrow road then we can automatically rule out several million men right away (the column would be ridiculously long).

There is of course one point, the bridge over the Hellespont, which the whole army (minus the European contingents picked up later) must cross in one long column, ridiculously long or otherwise. There are two bridges, but Herodotos informs us that all the army crosses one bridge, the baggage train using the other one. It took seven days and nights. Unfortunately, IIRC he doesn't say how wide the bridges were. I leave it to others to make the assumptions and do the arithmetic as to how many men and horses could cross a reasonable-width bridge in the time allowed - I'm sure it's been worked out before.

[Justin Swanton]

If it can be proven that the entire army had to march along a single track or narrow road then we can automatically rule out several million men right away (the column would be ridiculously long).

There is of course one point, the bridge over the Hellespont, which the whole army (minus the European contingents picked up later) must cross in one long column, ridiculously long or otherwise. There are two bridges, but Herodotos informs us that all the army crosses one bridge, the baggage train using the other one. It took seven days and nights. Unfortunately, IIRC he doesn't say how wide the bridges were. I leave it to others to make the assumptions and do the arithmetic as to how many men and horses could cross a reasonable-width bridge in the time allowed - I'm sure it's been worked out before.

Patrick did it somewhere: given the length of the boats and consequent width of the bridge and the time period, the Persians could operate at 25% efficiency and still get the entire army across with ease. I'll find the exact post.

[Erpingham]

It might be an idea to approach the subject from the angle of probability, i.e. we have the primary sources which all give the Persians huge numbers. Question then is to see if there is any insuperable obstacle to the Empire raising, supplying and moving armies of this size. If there are no insuperable obstacles then the burden of proof is on the other side: the sources can be assumed to be substantially correct unless proven otherwise.

Anything that is not impossible could happen.  What happens most of the time is a tiny subset of this.  It is best for those arguing for the outlier to make a case why, on this occassion, the nearly impossible is in fact the most likely case.

Nearly impossible?

A rather obvious take on "If there are no insuperable obstacles", I think.  Once you start talking about cases which aren't actually impossible, you can rapidly lose sight of the probable.  In history, it seems to me, we are looking at "the balance of probability" not "beyond all doubt" most of the time.

[Justin Swanton]

It might be an idea to approach the subject from the angle of probability, i.e. we have the primary sources which all give the Persians huge numbers. Question then is to see if there is any insuperable obstacle to the Empire raising, supplying and moving armies of this size. If there are no insuperable obstacles then the burden of proof is on the other side: the sources can be assumed to be substantially correct unless proven otherwise.

Anything that is not impossible could happen.  What happens most of the time is a tiny subset of this.  It is best for those arguing for the outlier to make a case why, on this occassion, the nearly impossible is in fact the most likely case.

Nearly impossible?

A rather obvious take on "If there are no insuperable obstacles", I think.  Once you start talking about cases which aren't actually impossible, you can rapidly lose sight of the probable.  In history, it seems to me, we are looking at "the balance of probability" not "beyond all doubt" most of the time.

My point is assuming a near impossibility when grounds for one have not yet been established. It is impossible for a 3-million-man army to march along a single narrow road or track, and that to the best of my knowledge is the principle argument for discounting large Achaemenid armies. But very large groups of people like the Helvetii have migrated cross country without roads and lacking any sophisticated logistics system.

If the ground is reasonably flat (somewhat sloping is not a problem) and has been cleared of trees and undergrowth then one can march very wide. Assume an army of 3,5 million men split evenly between 3 avenues each 200 yards wide, with each man occupying a space of 2 x 2 yards, and you get 3 columns each 23.33 km or 15 miles long. This is hypothetical but doable. The columns don't necessarily all meet at the coast each evening but food can be sent to prearranged campsites beforehand. It would take careful planning and local knowledge of the terrain but it could be done without teetering on the edge of nearly impossible.