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

[Jim Webster]

It would help if we take the time frame into account. Xerxes' 3.4 or 5.4 million man army doesn't eat a third or half or more of the available stocks of the population in Thrace and Greece. The army takes about 2 months to travel from the Hellespont to Greece. That's 16,7% of a year, hence 16,7% of the annual food requirement each way - say 8,4% passing through Thrace and 8,4% passing through Macedonia. It also feeds partly off the food dumps and partly off considerable supplies ferried over by the fleet (considerable because when the fleet could no longer function the army was in immediate trouble). I'm guessing Xerxes intended to strip Greece proper to lay up further stocks for the return journey. It is not unreasonable to assume that the allied tribes/nations the Persians passed through were not actually required to supply more than about 10% of their annual harvest, which is something they could manage.

I was taking the population as 4 million, so assuming they are assiduous in their response to orders, I assumed that they might produce an extra 10% surplus, which is 400,000 men a year. (Which given the average fluctuation in yields because of weather, is quite an achievement.)
Some of this surplus would be eaten during the four year period by the Persian garrison (and their servants, slaves, horseboys, horses etc) in the area or the crews of any Persian naval presence. Some of it will be eaten by the roadbuilders and canal diggers, those imported into the area to physically construct the depots. Some of it will probably be drawn on by local forces mustering to join the army of Xerxes. At the end of the four year period, when Xerxes arrives with his army, there will be some stockpile still left, but  I wouldn't factor it in as a major source of supply for the however many million men crossed into Europe

[Justin Swanton]

It would help if we take the time frame into account. Xerxes' 3.4 or 5.4 million man army doesn't eat a third or half or more of the available stocks of the population in Thrace and Greece. The army takes about 2 months to travel from the Hellespont to Greece. That's 16,7% of a year, hence 16,7% of the annual food requirement each way - say 8,4% passing through Thrace and 8,4% passing through Macedonia. It also feeds partly off the food dumps and partly off considerable supplies ferried over by the fleet (considerable because when the fleet could no longer function the army was in immediate trouble). I'm guessing Xerxes intended to strip Greece proper to lay up further stocks for the return journey. It is not unreasonable to assume that the allied tribes/nations the Persians passed through were not actually required to supply more than about 10% of their annual harvest, which is something they could manage.

I was taking the population as 4 million, so assuming they are assiduous in their response to orders, I assumed that they might produce an extra 10% surplus, which is 400,000 men a year. (Which given the average fluctuation in yields because of weather, is quite an achievement.)
Some of this surplus would be eaten during the four year period by the Persian garrison (and their servants, slaves, horseboys, horses etc) in the area or the crews of any Persian naval presence. Some of it will be eaten by the roadbuilders and canal diggers, those imported into the area to physically construct the depots. Some of it will probably be drawn on by local forces mustering to join the army of Xerxes. At the end of the four year period, when Xerxes arrives with his army, there will be some stockpile still left, but  I wouldn't factor it in as a major source of supply for the however many million men crossed into Europe

Reread my last but one post. A careful reading of the Thasian incident shows that the local Greeks supplied the Persian army only the occasional meal and did not feed it on a daily basis. Most of the army's food had to come from elsewhere.

[Jim Webster]

Reread my last but one post. A careful reading of the Thasian incident shows that the local Greeks supplied the Persian army only the occasional meal and did not feed it on a daily basis. Most of the army's food had to come from elsewhere.

An occasional meal might be possible. I agree entirely the food had to come from elsewhere
One problem with the logistics is we don't know how many men had to be fed in the four years lead up to the invasion. It might have been possible for them to be supported locally

[Erpingham]

I was taking the population as 4 million,

Estimates of the Classical Greek population I can find online vary from 3-15 million but the more considered seem to fit in the 8-12 million range.  This would mean Northern Greece in the coastal strip boasted half to a third of the Greek population.  Given the fact that the more densely populated bits were Southern Greece, Asia Minor and Sicily, this seems unlikely.

[Jim Webster]

I was taking the population as 4 million,

Estimates of the Classical Greek population I can find online vary from 3-15 million but the more considered seem to fit in the 8-12 million range.  This would mean Northern Greece in the coastal strip boasted half to a third of the Greek population.  Given the fact that the more densely populated bits were Southern Greece, Asia Minor and Sicily, this seems unlikely.

The figures I got were 12.5 for Greece and 2.5 for Ionia, but Macedonia was 4.
So to give a positive spin on things and to chose figures that would give some hope of them being able to contribute, I went for 4 million for the strip of Greece,plus those bits of Macedonia and Thrace that are involved 

but it is a very generous estimate

[Erpingham]

The figures I got were 12.5 for Greece and 2.5 for Ionia, but Macedonia was 4.

I did spot the estimate for Macedonia of 4 million but it was tagged as Hellenistic, when Macedon was both larger and more economically active.  However, it is all rather gestimated at the best of times.  I think on further reflection I'd revise my population estimate of the region upwards from 1 million though.  How much of it is in range to be involved with the Great Army I don't know.  Most of the cities and plains are in striking distance of the coast I think, so the economy is probably weighted that way too.

[Jim Webster]

The figures I got were 12.5 for Greece and 2.5 for Ionia, but Macedonia was 4.

I did spot the estimate for Macedonia of 4 million but it was tagged as Hellenistic, when Macedon was both larger and more economically active.  However, it is all rather gestimated at the best of times.  I think on further reflection I'd revise my population estimate of the region upwards from 1 million though.  How much of it is in range to be involved with the Great Army I don't know.  Most of the cities and plains are in striking distance of the coast I think, so the economy is probably weighted that way too.

Yes, and none of the area along that north coast strikes me as a grain basket. The simple economics of animal transport mean that once you are hauling the grain more than so many days, you might as well ship it in from Egypt by sea.

[Justin Swanton]

I was taking the population as 4 million,

Estimates of the Classical Greek population I can find online vary from 3-15 million but the more considered seem to fit in the 8-12 million range.  This would mean Northern Greece in the coastal strip boasted half to a third of the Greek population.  Given the fact that the more densely populated bits were Southern Greece, Asia Minor and Sicily, this seems unlikely.

The figures I got were 12.5 for Greece and 2.5 for Ionia, but Macedonia was 4.
So to give a positive spin on things and to chose figures that would give some hope of them being able to contribute, I went for 4 million for the strip of Greece,plus those bits of Macedonia and Thrace that are involved 

but it is a very generous estimate

Let's leave it a 4 million and make the Persian army 4 million strong. Using the Thasian coastline as a rough rule, the Persians demand one meal from their hosts every 8 days. They spend 60 days marching to Greece so require 8 meals. The Balkan Greeks grow/import enough food to feed themselves for a year. The Persians take 8 days of that food during the outward journey and, presumably, would take 8 days food during the return trip had they conquered Greece. That's 16 days food out of a stockpile meant for 365 days. Thus, 16 ÷ 365 x 100 = 4,4% of the harvested grain. The locals would not even have to grow more food to make it work, just tighten their belts a bit.

[Erpingham]

So you are going with a proportion of food locally sourced to imported at approximately 1:8?  Import levels will be in the region of 200,000 tonnes.

[Jim Webster]

Let's leave it a 4 million and make the Persian army 4 million strong. Using the Thasian coastline as a rough rule, the Persians demand one meal from their hosts every 8 days. They spend 60 days marching to Greece so require 8 meals. The Balkan Greeks grow/import enough food to feed themselves for a year. The Persians take 8 days of that food during the outward journey and, presumably, would take 8 days food during the return trip had they conquered Greece. That's 16 days food out of a stockpile meant for 365 days. Thus, 16 ÷ 365 x 100 = 4,4% of the harvested grain. The locals would not even have to grow more food to make it work, just tighten their belts a bit.

The problem is we have to remember the 'Persians' already there. Somebody has been feeding the engineers etc.
This meal is on top of that.
Also when you look at the island itself it's known for olive oil, wine and honey, not grain growing. The hinterland is Thracian so you're not talking about major civilised agricultural areas. I suspect the Thasians imported a lot of grain, and being the wealthy owners of gold mines, imported a bit more to make a show of loyalty.
The Thracians on the mainland aren't known as grain exporters.

Yes, some communities could and would have contributed, I'd say West of the Thasians might hold out more hope.

I'm coming to think that even if the Persians had sent an army of 40,000 into this area, they'd probably have depended largely for supplies on the sea. Unless it was a pacification campaign where you didn't are how many villages you sacked and devastated.

[Justin Swanton]

So you are going with a proportion of food locally sourced to imported at approximately 1:8?  Import levels will be in the region of 200,000 tonnes.

Locals: 12%; depots and ships: 88%. Those figures make sense in the context of the Thasian incident. For 4 million men that's 200 000 tons, yes. 80 50-ton ships beach and offload 4000 tons a day and you get 240 000 tons if they operate every day of the campaign. If the transport fleet numbers 800 ships and they can work 7 days out of 8 it is feasible without taking the depots into account. Take them into account and the ships can do the job in 6, 5 or 4 days out of 8.

[Justin Swanton]

Let's leave it a 4 million and make the Persian army 4 million strong. Using the Thasian coastline as a rough rule, the Persians demand one meal from their hosts every 8 days. They spend 60 days marching to Greece so require 8 meals. The Balkan Greeks grow/import enough food to feed themselves for a year. The Persians take 8 days of that food during the outward journey and, presumably, would take 8 days food during the return trip had they conquered Greece. That's 16 days food out of a stockpile meant for 365 days. Thus, 16 ÷ 365 x 100 = 4,4% of the harvested grain. The locals would not even have to grow more food to make it work, just tighten their belts a bit.

The problem is we have to remember the 'Persians' already there. Somebody has been feeding the engineers etc.
This meal is on top of that.
Also when you look at the island itself it's known for olive oil, wine and honey, not grain growing. The hinterland is Thracian so you're not talking about major civilised agricultural areas. I suspect the Thasians imported a lot of grain, and being the wealthy owners of gold mines, imported a bit more to make a show of loyalty.
The Thracians on the mainland aren't known as grain exporters.

Yes, some communities could and would have contributed, I'd say West of the Thasians might hold out more hope.

I'm coming to think that even if the Persians had sent an army of 40,000 into this area, they'd probably have depended largely for supplies on the sea. Unless it was a pacification campaign where you didn't are how many villages you sacked and devastated.

Work on the presumption Xerxes had all the figures we have discussed here and knows it is not a good idea to starve his vassal states to death (it makes them disgruntled and rebellious). He can feed his engineers by sea during the 4 years they work at the canal, etc. The Thasians import food, fine, the point is their economy is sufficient to feed them and spare 4,4% for a transient Persian army. Bear in mind the meal cost them 400 talents. Their mines made them between 200 and 300 talents of silver a year, so 4 years is adequate time to store up enough lucre to do some serious buying in preparation for the arrival of the Persian host (and I doubt they bought all their own food from their silver).

[Erpingham]

For 4 million men that's 200 000 tons, yes. 80 50-ton ships beach and offload 4000 tons a day and you get 240 000 tons if they operate every day of the campaign. If the transport fleet numbers 800 ships and they can work 7 days out of 8 it is feasible without taking the depots into account. Take them into account and the ships can do the job in 6, 5 or 4 days out of 8.

Rome imported around 420-30 ktonnes a year, using fixed infrastructure and distribution, as a comparison.

[Justin Swanton]

For 4 million men that's 200 000 tons, yes. 80 50-ton ships beach and offload 4000 tons a day and you get 240 000 tons if they operate every day of the campaign. If the transport fleet numbers 800 ships and they can work 7 days out of 8 it is feasible without taking the depots into account. Take them into account and the ships can do the job in 6, 5 or 4 days out of 8.

Rome imported around 420-30 ktonnes a year, using fixed infrastructure and distribution, as a comparison.

The Persians move 200 000 tons in two months. The Romans move 400 000+ tons in 8 months (sailing is closed for 4 months of the year). That's over twice as much grain in a period 4 times longer, which means the Persians move their grain nearly twice as fast. If they've dedicated pretty much their entire merchant fleet to the job and have built many extra ships as well, it's not inconceivable.

[Patrick Waterson]

I do not wish to disturb a positive line of discussion, but do want to sort out one point.

Patrick please be sensible

A community doesn't just hand over its entire food stocks. They are merely condemning themselves to slow, lingering and unpleasant death.

Herodotus mentions grinding corn for 'many months' into flour.  This indicates that as of early spring they had 'many months' of corn available to grind.  Whether this was their entire stock is another matter - probably not, because as you rightly point out Herodotus does not mention mass starvation among the local population (although the returning Persian army is subject to mass starvation).

similarly a population of perhaps four million does not have the food stocks to feed an army of six million with hangers on. If they have a 10% surplus that will be about it. These are subsistence economies! In some years they'll struggle to feed themselves!

Everything I have read about this (5th century BC) period convinces me these are not subsistence economies; they are economies producing a comfortable surplus which allows extensive storage, fuels plenty of ongoing wars and the sources conspicuously lack mention of famine except when a city is under prolonged siege.  A good deal of polis organisation seems to have gone into provisioning the home city for a siege, and this would give a significant reserve upon which to draw.  It would of course have to be turned over on a regular basis to avoid spoilage, but later in the century cities like Potidaea could hold out for over a year without reprovisioning.

It is also not a case of feeding six million men for an indefinite length of time: it is about feeding them for a day.  If one person has six months of surplus food (180 person-days) they can feed 90 persons for two days or 180 for one day.  So if 90 people drop in for one day the individual is down to three months of surplus food - not an impossible or life-threatening situation.

Given this 1:90 sustain-for-a-day ratio, a population of (say) 1 million would be able to host a transient 6 million who stayed only briefly.  It would be a burden, but not a killing one.