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Ok, the population of Greece during the classical or hellenistic era was around 2.5 million in total,including the slaves.Athens had around 700.000 including the slaves and metoikoi.Athens could gather up a force of 60-80.000 hoplites.When they invaded Sicily they send 40.000 and of course they kept reserves back home to defend the city.And because they were in war with Sparta the reserves must have been around 10.000 or maybe more.

Due to the fact that in many city-states the hoplites could only be registered citizens and not metoikoi,the numbers of the armies were not as big as if they gathered up the metoikoi and slaves too.Sparta did that because they had too few citizens,so they had to fill in with metoikoi.

I have searched the net about the Persian Empire demographics but couldnt find anything.The information that we have about the persians is sparse anyway.But surely the population may have exceeded 10 million.If Greece was 2.5 million then Persia alone may have been around that number or more.Then we have the Bactrians,the Egyptians,the Parthians,the Indians e.t.c and the various barbaric tribes.So the population could have been at least 10 million or maybe way more.

The Persians used all of their population as soldiers, meaning notr only citizens as in Greece.So if they wanted they could gather up at least a million of army or even more.The only problem was the supplies as Paralus said.But from the sources we get that the Persian army was accompanied by tens or hundreds of thousands of slaves,and animals that carried everything with them.The ony problem could be the water but this could be easily found.Darius knew where to go to find supplies that he may have needed and no one could stop him.

On the other hand a big army is moving slowly.But that is also shown at the sources.The timeframes match.It took long for Xerxes to cross Greece and that shows that the army must have been huge.Darius moed his army easier because Asia minor and Persia is full of plains where the army could move faster.

nevertheless there is absolutely no reason not to accept the numbers given by the sources regarding the persian army.The Persian Empire could gather up even larger armies,and judging by the fact that it is mentioned that Alexander prefered to have a smaller army that could move faster ,we can assume that the "smaller" is in comparison with the persian army.

Saying that the persian army was around 100.000 is absolutely wrong and underestimating the Persian Empire's population.At gaugamela Darius knew that if he would lose the battle then he could lose the Empire.Would he only gather up 100.000 troops?Or even 300.000 when he could gather up more?

Again the demographics of the empire support the numbers that are given in the sources.

Hi Efstathios,

I'm absolutely no expert on population and army numbers. However, there appears to be one crucial point missing in your post, which someone (I think Paralus) made in reference to Gaugamela - the fact that, irrespective of the numbers, or the fact that the army moved slowly, victualling an army of such a great size would be all but impossible. One can have the numbers, but the longer they take to get to their destination, and the longer they have to wait for battle, the harder it is to feed them.

I wonder whether, if the Persian army was so huge at Gaugamela, that one of the reasons why Alexander won was because they were all so darned hungry!

ATB

Marcus, the Persian Empire had a different system for warfare.While the greeks were counting on their good training and armor and courage,the persians were counting mainly on numbers.And indeed they were so many that they conquered almost the entire Asia.Amd as they conquered their army grew in numbers too.

The egyptians had a good army too.The indians too.Do you think that the persians could have conquered all these people if they didnt have a huge army?Do you think that they would have conquered these people with their light armors and their not so high morale and courage?Ponder about that a little bit.

And maybe Cyrus inspired morale and courage to the persian army but that doesnt necessarely apply to Xerxes or Darius.

Efstathios wrote:Athens had around 700.000 including the slaves and metoikoi.Athens could gather up a force of 60-80.000 hoplites.When they invaded Sicily they send 40.000 and of course they kept reserves back home to defend the city.And because they were in war with Sparta the reserves must have been around 10.000 or maybe more.

G'day Efstathios!

There's a classic Australian film called "The Castle". It's full of memorable quotes but, the pertinent one would be "He's dreamin'!"

There is no way that Athens GÇô at any time in antiquity GÇô could muster 60-80,000 hoplites. That is plainly inconceivable.

Whilst it is difficult to precisely number Athens' population at any particular time, many informed guesses have been made. Of those guesses, none that I have read approach 700,000. At the hight of its pomp GÇô the mid 450s GÇô the Athenian population is put at 474,000 (P Green, Armada From Athens, Doubleday, 1970), of which some 16,000 are estimated to be of the hoplite class. Considering that in 490, facing annihilation by Persia, Athens could muster only 10,000 hoplites at Marathon (leaving the old and the too young at home), this would seem correct. As well, in 457, facing the largest Peloponnesian army in central Greece since Plataea, Athens (Thuc, 1.108) mustered GÇô in Thucydides' words GÇô "their whole army" of 14,000 hoplites which included "1,000 troops from Argos" and "contingents from their allies". The numbers appear correct.

By the start of the Peloponnesian War those figures become 463,000 and 13,000 hoplites of serving age (20-40) as well as 16,000 of the old and the too young (D Kagan, Peloponnesian War, Viking 2003).

As to the Sicilian disaster, Athens GÇô in the first expedition GÇô contributed some 16,780 men out of an armament conventionally estimated at about 27,500-28,000. This breaks down to: 1,500 hoplites (of 4,400), 150 peltasts, 700 marines and a small amount of cavalry. The rest were "sailor swill" of the lowest classes. In the relief expedition led by Demosthenes, Athens supplied some 1,200 hoplites and rowers to the tune of some 9,000. A far cry from 40,000.

In the fourth century the population of Athens was a far cry from its heyday. The plague and the war had decimated Athens' manpower. The plague alone is estimated to have removed one third of the population. We're talking something more than a generation gone here. The singular indicator being the force mustered at Chaeronea in 338. Here Athens managed some 10,000 hoplites for the "do or die" showdown with Philip. Christian Habicht (Athens from Alexander to Antony, Harvard 1997) puts it nicely:

As darkness fell that summer night in 338, 1,000 Athenians lay dead on the battlefield at Chaeronea. Another 2,000 had fallen into Philip's hands as prisoners of war, heavy losses for a state whose total adult population (citizens) numbered at most 30,000, the old and the unfit included

Going on the fact that the "knight" (hoplite) class represents some 2.8-3% of the total, that would put the population at somewhere between 300-340,000. A far cry from 700,000 and very much in line with estimates for the period.

It is arguable in the extreme that the Persians "used all of their population" as soldiers. They levied contingents from their territories but, they did not fit them out. Again, you find those who serve as infantry need to be in a position to "afford" to (unless, of course, you are an "apple bearer"). In my readings, I have yet to see Persian armies of conquest (Cyrus, Cambeses and Darius I) numbered in the hundreds of thousands (hyperbolic Herodotus aside).

Efstathios wrote: The Persians used all of their population as soldiers, meaning notr only citizens as in Greece.So if they wanted they could gather up at least a million of army or even more.The only problem was the supplies as Paralus said.But from the sources we get that the Persian army was accompanied by tens or hundreds of thousands of slaves,and animals that carried everything with them.The ony problem could be the water but this could be easily found.Darius knew where to go to find supplies that he may have needed and no one could stop him.

The fact is that an army must be fed and it must be bivouacked and it must be watered. To state that "tens or hundreds of thousands of slaves and animals" attended it is nonsense. That only adds to the mouths and guts in need of filling. The sources suggest cavalry at Gaugamela to the tune of some thirty thousand or more. It takes more that a bale of hay to feed some thirty thousand horses. So we have "thousands" of mules to carry it, problem is, they too need to eat it. It's a never ending circle.

Three hundred years before Christ the logistics of supply that we take for granted did not exist. There is no way the arid plains of north-western Iraq would support an army of 300-500,000 for more than ten minutes. It is the local population who must do it GÇô must go without. It would devastate the area.

I'd suggest you read the detail of the Iranian campaigns of Antigonus and Eumenes (Paraetacene and Gabiene) in 317/6 to see what measures needed to be taken to feed and water armies totalling (both together) some 70-85,000 men and how debilitating such numbers were on the country they operated in. As well, there are reasons that had little to with numbers and much to do with court politics for Darius choosing the battleground of Gaugamela.

Efstathios wrote:The sources report 110-120.000 total number of Alexander's troops by the time of the campaign in India.Most of them where persians,bactrians e.t.c.

Where do the sources place those "persians, bactrians e.t.c" at the Jhelum?

Eftsa Hail

I gotta stand by your remarks here. As you say the Persian Empire was huge and the man powere must have been multiples of Greece. Darius faced Alexannder twice in full scale battle and I am sure the guy must have mustered as many forces as he could. Lets face it you dond go to a shootout with a gunslinger using a Bowie Knife. Darius and the Persian Empires neck was on the line Particulaly at Gaugamella. Maybe at Issus Darius was complaicent with lesser numbers. He even turned up with his family to watch what he must have thought a walkover.

Lessons learned Darius bolstered his Cavalry. And even selected a prefered battle field. He must have had a huge host knowing what had happened at Issus. Its silkly to say a huge army cant be sustained in its own back yard. The Monghuls marched all the Way from Mongolia to Europe with excess of 200 000 men. I doubt there was a Tesco or any friendly suppliers for those boys. Maybe the numbers in Millions is an egageration but hundreds of thousands definately not. The Romans alone had 80 000 soldiers at Canea and that was only one battle.

Kenny

kennyxx wrote: Maybe at Issus Darius was complaicent with lesser numbers. He even turned up with his family to watch what he must have thought a walkover.

G'day Kenny.

He turned up with his family, I suspect, for totally different reasons. One must remember that Darius - that certain Codomannus - did not come by the throne in any "normal" succession. He was not of the direct royal line as Bagoas had already seen to its extinction. As such, there were many other Persian nobles with similar, if not better, claims to his throne. Many of these were with him at Issus and some - by neccessity - were not.

His immediate family most certainly was though. And, one suspects, for good reason.

Efstathios wrote:Marcus, the Persian Empire had a different system for warfare.While the greeks were counting on their good training and armor and courage,the persians were counting mainly on numbers.And indeed they were so many that they conquered almost the entire Asia.Amd as they conquered their army grew in numbers too.

The egyptians had a good army too.The indians too.Do you think that the persians could have conquered all these people if they didnt have a huge army?Do you think that they would have conquered these people with their light armors and their not so high morale and courage?Ponder about that a little bit.

And maybe Cyrus inspired morale and courage to the persian army but that doesnt necessarely apply to Xerxes or Darius.

Yes, but there are large numbers and there are large numbers - I don't know whether the Egyptian army was any good, but they also had very light arms and armour, as did the Indians (apart from elephants, which weren't half as useful in battle as they looked). Even if the Egyptians were good, if they could only field, say, 40,000 men, then the Persians didn't need half a million to conquer them ... and if the Egyptians weren't ready and therefore hadn't mustered all their troops, etc. etc. - the fact is, the Persians didn't necessarily need such large armies.

But, forgive me saying so, that isn't really the point I was making - the fact is, it would be all but impossible to sustain such a huge army in the field. Sure, they had loads of baggage - but remember that every pack animal also has to feed, and therefore something has to carry its feed, as well as the food it's supposed to be carrying. There comes a point where it just isn't feasible.

And the larger the army, the longer it takes to march anywhere, so it's in the field for longer ... it becomes a vicious circle.

All the best

Efstathios wrote: The egyptians had a good army too.The indians too.Do you think that the persians could have conquered all these people if they didnt have a huge army?Do you think that they would have conquered these people with their light armors and their not so high morale and courage?Ponder about that a little bit.

Actually, at the time of the Persian conquest (525 BCE), the Egyptian army was but a shadow of its former self. Alan Lloyd, in The Oxford History of Ancient Egypt (Shaw, Ian, Ed. The Oxford History of Ancient Egypt. Oxford: Oxford University Press, 2000), states that the standing army of the Late Period was comprised of two corps -- the machimoi, or native militia, and the mercenaries. Pharaoh Ahmose II made extensive use of Greek heavy infantry, along with hired Libyan, Nubian, and Jewish troops. Indeed, the core of the machimoi were themselves Egyptianized Libyans from the Western Delta. Native Egyptians formed a levy, called at times 'an unorganized rabble of artisans', with minimal armor or training. However, the Egyptians possessed a formidable navy and were incredibly skilled at creating defensive fortifications (not unexpected, as they were architects born and bred).

Ahmose used his Greeks mostly to balance the power of the unruly machimoi (he came to power thanks to an uprising in this Egyptian warrior class); by the end of his reign Greeks were stationed at Memphis and in desert camps outside Pelusium. A contingent of Jewish mercenaries were posted at Aswan on the border with Nubia, and the machimoi manned forts on Egypt's western border.

Unfortunately, we have no records describing the battle at Pelusium, no troop counts or dispositions beyond the fact that both sides possessed hoplites in considerable quantities, profusions of levies, and that for some reason the Persians were unable to get the upper hand with either cavalry or archers (their preferred tactic at the time) and had to fight a hand-to-hand battle. According to Herodotus, Egypt might have thrown them back had Psammetichus III not gotten spooked and fled to Memphis (shades of Darius at Issus and Gaugamela?).

In the years leading up to Alexander's arrival, the Egyptians became more and more dependant on foreign mercenaries (Spartans and Athenians, in the main); by 341 or so, their best fighters were guerillas who were intimate with the landscape, fairly easy pickings for Artaxerxes III's mixed Persian-Greek forces once the problem of logistics was handled.

Best,

Scott

Just a couple of quick notes on army numbers and supply chains necessary to sustain them.

The normal grain ration for an Athenian rower manning a trireme in the navy of the fifth and fourth century was one choinix (or 1.09 litres/ 0.83kg). This GÇô as well as water GÇô was considered sufficient to sustain the best rowers of the time. This does not, of course, take account of any other foodstuffs (onions, dried fish, figs, etc) that may well have been supplied.

Should we accord Darius a mid range figure of 300,000 men at arms at Gaugamela, the extrapolation becomes 249,000kg of grain GÇô and grain only GÇô per day. Should we further assume that this host was gathered GÇô for a period of say three to five weeks GÇô somewhere northwest of Babylon and the western high plains of Media, then we can safely assume that some 5,229,000 GÇô 8,715,000kg of grain was ferried to it.

Given that these men would likely consume GÇô on rationed basis GÇô possibly 1.5 litres of water per day, then we can see an army of 300,000 swallowing some 450,000 litres per day. This before we come to the animals with it and the Great King's somewhat more cosmopolitan tastes.

Curtius tells that when the Macedonian army found itself engaged in a siege at Miletus, the situation was grave as the army had descended upon the fields of Hellespontine Phrygia as a locust. Even allowing for Curtian exaggeration, it would be plain to any commander that going back the way it had come was GÇô from a supply point of view GÇô out of the question. Very similar situations obtained for both Eumenes and Antigonus on the Iranian high plains during 317/6. Both needed to withdraw and "operate" in areas untouched by either army. Eumenes had to "scatter" his forces to their winter camps so as the land could feed them.

An army numbering between 300-500,000 will have descended onto the plains of Media and soaked up the resources as a roll of tissue paper soaks up a drip.

Stil the Persian army could follow specific routes in order to find enough food and water.But i guess they didnt feed only from the places they had passed by.They must have carried supplies with them to last them long enough when they couldnt find anything to eat at deserts or plains.And i think that would be enough.They also must have had oxes (did i spell it right? you know, the cow-similar animal),or animals that could feed from the earth,grasslands e.t.c to carry the food and water.The army was not traveling fast anyway.And thats why Alexander said that with a small army he could move faster.

Plus the Great king would have issued an order to all the Kingdom for the farmers to provide them with enough food,or better to cultivate specific quantities if that was possible and maybe with expenses paid by the Kingdom.

That goes for the campaign in Asia.But when the Persians landed in Greece i think they could have found enough food easier.And anyway that campaign took much longer.The army was moving from place to place very slowly and that wasnt due to the resistance that they found of course.Most of the northen cities didnt give much of a fight.That explains it.The army needed supplies so they would stay at places until they found the quantites of food they wanted.So they could have been 800.000 or million.

As for the Asian campaign ,they could have been 300.000 or even 500.000.I dont know.But surely Darius would get as many as he could in order to confront Alexander at Gaugamela.And especially when he had his Wife and daughters there.

Efstathios wrote: Plus the Great king would have issued an order to all the Kingdom for the farmers to provide them with enough food,or better to cultivate specific quantities if that was possible and maybe with expenses paid by the Kingdom. As for the Asian campaign ,they could have been 300.000 or even 500.000.I dont know.But surely Darius would get as many as he could in order to confront Alexander at Gaugamela.And especially when he had his Wife and daughters there.

GGÇÖday Efstathios.

The problem at this stage for Darius is three fold. First his family (and those of other nobles, one might suggest, who were at Damascus) were hostage; second the entire western half of the empire was gone; thirdly he was in a precarious position as king.

The hostage situation meant that decisive offensive action was rendered far too dangerous. Better to attempt negotiation and if all else fails, fight the GÇô necessarily GÇô defensive battle that must come. As such, he was always at the mercy of a brilliant tactician in Alexander.

From the second come two things. The first is that all those western satrapies are lost. It follows that there will be no army recruitment from the entirety of Asia Minor, Coele-Syria and Egypt (barring any renegade escapees). Indeed, most of the Greek mercenaries the empire GÇô in its decline as a military power GÇô had used to fight its wars (Egypt for example) had bled away. The second relates to your GÇ£all the kingdomGÇ¥ phrase. Darius retained the rich, irrigated farmlands of Babylon and some in Iran. He had lost the produce of the whole of Asia Minor, the Lebanon and GÇô most alarmingly GÇô the GÇ£bread basketGÇ¥ of the Ancient Mediterranean, Egypt. These Alexander now had in his logistics companyGÇÖs kit bag. In fact, most of PersiaGÇÖs military actions since the Greek excursus (480) involved regaining and subduing Egypt GÇô in recent times with Greek troops.

The third needs its own paragraph. Darius had not come to power in any ordinary accession. He was there because the others GÇô who were more directly in line GÇô had been murdered. He was not pure Achaemenid stock and did not have any significant military background. In simple form: there were other nobles who thought themselves as deserving of the upright tiara as him GÇô if not more so. He could not trust any to command in the field and so at Granicus we have a shared command. Afterwards Darius appoints Memnon, trusted due to the fact his family is hostage at court. At Issus, almost all the nobility is present (aside from those who by necessity must remain in the capitals) and Darius brings his family along GÇô no point leaving them behind as possible hostage material. Unfortunately, they became hostages but, hostages of the Macedonian GÇ£pretenderGÇ¥. XerxesGÇÖ rather incontinent flight from Greece after Salamis indicates the position a defeated king might find himself in. Hence Darius was not ever going to move far from the empireGÇÖs centre for what became Gaugamela. (Further info found in Alexander in Fact and Fiction, Bosworth, ed)

Efstathios wrote:But when the Persians landed in Greece i think they could have found enough food easier.And anyway that campaign took much longer.The army was moving from place to place very slowly and that wasnt due to the resistance that they found of course.Most of the northen cities didnt give much of a fight.That explains it.The army needed supplies so they would stay at places until they found the quantites of food they wanted.So they could have been 800.000 or million.

It was indeed a rather GÇ£sereneGÇ¥ advance. If we are to take HerodotusGÇÖ description at face value, this was mostly due to the kingGÇÖs penchant for display and the finer GÇô dining GÇô things in life. It is doubtful in the extreme that his force numbered 800,000-1,000,000 though. Most estimates put it at somewhere between 90,000 (too low methinks) to 350,000. Somewhere between 220-260,000 (not including the fleet) would be my guess. Much of the victualling was carried out by the merchantmen of the fleet GÇô one of the reasons why many departed after its defeat.

In the end, Mardonius hand picked his best troops (the Medes, Persians, Sake and Iranians) to the number of some 30,000 or so. These were augmented by Greek Medisers (Boeotia et al). Again, if we are to take Herodotus at his word, the troops he originally wanted for the mission.

To the Greek city states GÇô none of whom outside of Athens, Sparta and possibly Thebes could put 10,000 into the field at any one time GÇô the sight of some 120-190,000 in the field in Greece will have seemed a million. The Greek alliance (minus Boeotia) could muster only some 53,000 GÇô of which 30 - 35,000 or so will most likely have been hoplites GÇô for the decisive battle. The numbers of the Persians will have seemed fantastic.

At Plataia the greeks put 100.000 soldiers.And surely they knew how to count their troops.So i think that they could calculate easier large numbers of enemies.And even if Herodotus made a mistake about the first war, at the second (Thermopylaie,Salamis,Plataia) there is a better comparisson to be made.At Plataia the Persians were 300.000.And these were the ones that were left behind.

If we assume that the King left behind 2/3 of his army then the initial size would be about 450.000.If he left behind 1/3 then it would be 900.000.He was fleeing from Greece and he left the 300.000 back just in case they could win at Plataia.And i dont think he would leave more than half of his army behind.So my guess is that the initial army must have been around 600.000.Plus the slaves e.t.c around a million.There you have it.

This could go on for years Efstathios. In fact it has.

If one is to use Herodotus' figures then stick with them. That would give you 1,700,000 Persian infantry. That is a plainly preposterous number. Personally, I agree with the theory that postulates Herodotus confusing the Persian denominations chiliarch and myriarch. Such confusion would result in multiplying all Persian forces by a factor of ten. Thus we arrive at 170,000 infantry and an army all up of some 210,000. General Sir Frederick Maurice walked the route taken by Xerxes and estimated it would support at most 210,000

Similarly, Herodotus tells of a Persian battle fleet of 1327 ships. By the time we reach Salamis, Herodotus rather unwittingly informs us that Persian naval superiority of numbers was barely maintained (Hdt, 8.13). Given that GÇô at the highest estimate GÇô the allied fleet numbered some 400 (and more likely 310-320), one needs to ask what became of the 1,327? The answer is GÇô on face value GÇô either that numeracy was not the historian's strong suit or we shouldn't disturb a great propaganda piece with disturbing fact. Which fact might be that some 674 ships were still waiting for the Great King at Sestos masquerading as a bridge?

If we accept Herodotus' totals for the Greeks at Plataea (some 53,000 hoplites) are we then bound to accept a total of 47,000 light armed? I myself find it unlikely that Sparta would send seven helots per hoplite GÇô more likely three. As well, Athens (and the other allies in the fleet operating at Mycale) will have contributed rowers to the fleet who may well have been peltasts. Either way, I find it difficult to accept 100,000 Greeks at Plataea GÇô on the allied side. As well, there seems little description of the part played by such a large number of light armed troops in the battle itself. In fairness, they may have been delegated to guard the passes in the Greeks rear.

Herodotus goes on to inform us that Mardonius had 300,000 (plus one imagines the Medising Greeks as well). Along with this, he describes the large "military stockade" he built to protect his troops. The area enclosed is 900 acres. Burn (Persia and The Greeks: The Defence of the West) interestingly notes GÇô when comparing same to Roman stockades GÇô that this would fit an army of some 60-70,000. Of this, there could be no more than 10,000 cavalry as this would seriously reduce space for the infantry. One supposes the other 230,000 were left to fend for themselves.

Finally Xerxes GÇô discounting the lurid fictions about his march home with the bulk of his army GÇô arrived at Sestos only forty-five days after setting off. This is, of course, in stark contrast to the time taken to march his army over. Not something he was likely to achieve in the company of some 300-400,000 troops.

Paralu hail

I really gotta take issue with the problem of suataining a large force. The Persians as we say were at home in there own back yard. There must have been Cities Granaries farms producers etc that would sustain. Even if not by force he could very well afford to pay for what he needed.

If as you say its impossible to sustain such a large force. Then how do you explain how Alexanders growing colony was sustained with supplies food water etc in a foreign even hostile country. Once Again the Khan dispatched 200 000 Mongul warriors horses and all to get all the wayn to Europe.

Although we had mechanical and modern technology. How hid The Uk sustain and feed the hundreds of thousands of soldiers waiting then embarking on the D Day landings as well as feed her population. You can argue that things logistically are impossible. Indeed the Million plus numbers are to far fetched but I wouldnt discount half a million men at Gaugamella at the battle Darius would have turned up with his grandad and his pet dog. He was fighting for his skin.

Kenny

kennyxx wrote:Paralu hail

I really gotta take issue with the problem of suataining a large force. The Persians as we say were at home in there own back yard. There must have been Cities Granaries farms producers etc that would sustain. Even if not by force he could very well afford to pay for what he needed.

If as you say its impossible to sustain such a large force. Then how do you explain how Alexanders growing colony was sustained with supplies food water etc in a foreign even hostile country. Once Again the Khan dispatched 200 000 Mongul warriors horses and all to get all the wayn to Europe.

Although we had mechanical and modern technology. How hid The Uk sustain and feed the hundreds of thousands of soldiers waiting then embarking on the D Day landings as well as feed her population. You can argue that things logistically are impossible. Indeed the Million plus numbers are to far fetched but I wouldnt discount half a million men at Gaugamella at the battle Darius would have turned up with his grandad and his pet dog. He was fighting for his skin.

Kenny

Unfortunately I really don't think you can draw a comparison with supply logistics in the 20th century - totally different ball game. The fact is, back yard or not, an army that size, moving pretty slowly, requires an enormous amount of food and water. It all has to be carried by something - horse, mule, waggon, whatever - and any pack animals also have to be fed, so they have to carry their own food as well as all the stuff for the army. There comes a point where the numbers just don't add up.

Once Alexander had installed a colony in a city, they lived off the land. But we're talking about a matter of hundreds of men, usually, at the most - the rest of the city populations were the natives who were living in the area already. So supply for them was a different kettle of fish altogether.

As for Genghis Khan (you're pretty keen on him at the moment, aren't you? ), I don't know about his supply chain, but I imagine that there wasn't much left in his wake ... and nobody records what happened to the people left alive behind him, and whether they then starved for lack of food. But, to be honest, the situation 1,500 years after Alexander is, again, totally different, and we can't really force a comparison unless we know much more about the agricultural and livestock situations in the areas the Mongols passed through.

All the best