The Number Problem in the Persian Wars 480-479 BCE

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Categories: Ancient
A four-part bronze horse bit, aggressively cleaned and patinad, in a museum display case
A bronze horse bit from the archaic in Rimini. Similar forms were still used by Achaemenid cavalry. Quoth the label: Rimini, Friano. Corredi funerari con elementi di carro e morsa di cavallo in bronzo. Prima età del ferro, VIII-VII secolo a.C.

Quite a few people interested in ancient warfare know an article by one F. Maurice on the water and roads at the Hellespont. After reading Herodotus’ story that Xerxes marched through the area with 1,700,000 infantry, 80,000 cavalry, and 20,000 charioteers and camel-riders and hiking around the countryside in summer, he argues that an army of 150,000 soldiers, 60,000 noncombatants, and 75,000 animals is the absolute maximum that could have been fed and watered in the area (paragraphs 10, 21, 33). I think this was the Major-General Sir Frederick Barton Maurice who was forced out of the British Army for political reasons in 1918, became a journalist and an advocate for veterans, and died on 1 May 1951. People cite it because he was an experienced staff officer who had walked the ground and talked to classicists like J.A.R. Munro. Its full of details such as that the British Expeditionary Force of 72,000 men, with railroads for supply but just horses for transport, needed 20 square miles for its camp in 1914 (the cavalry were stationed elsewhere and the motor vehicles had not yet arrived). But its certainly not the last say, and while he was talking to British classicists, a retired Bavarian general was preparing a study of the same problem and addressing their arguments.

One Robert von Fischer (d. 1937) commanded the 1st Royal Bavarian Landwehr Division in France from September 1914 to December 1915 and received the honorary title of Bavarian General of Infantry in 1917. He had similar military credentials as Maurice: he commanded a division on the Western Front for 16 months, Maurice served in the Tirah Expedition in Afghanistan, the Boer War, and briefly on the Western Front. And after examining the whole route and the problems involved, he felt that the Persian army was probably no more than 40,000 soldiers strong.

One fundamental problem is that for long stretches of the route, the Persians were forced to take a single road, such as their march along the Gallipoli Penninsula between the sea and steep hills. And if that is really a single road, with no grass at the side for the troops to march along while the baggage train follows the road, then an army of 10,000 infantry, 2,000 cavalry, and 700 two-horse carts will occupy at least 21 km of road. That is pretty close to a day’s march, so in his day the rule of thumb was to send ideally no more than one division (15,000 heads), if necessary an army corps (45,000 heads), and if there was no alternative two corps (90,000 heads) down a single road (pp. 298-299). When the head of that two-corps column halted, it would have to wait up to four days for the rest of the column to catch up. This way of “marching divided but fighting united” first became common in the Napoleonic Wars with the introduction of professional staffs trained to prepare maps and timetables and keep the different parts of an army in communication with one another (the Mongols in the 13th century also managed it). It is not what Herodotus describes. And so von Fischer pointed out the problem with saying “If Napoleon could invade Russia with several hundred thousand men, why couldn’t Xerxes invade Greece?”

According to Herodotus a land army of 1,700,000 infantry, 80,000 horsemen with a baggage train (Troß) of at least the same headcount- so twice the headcount as the German army employed against France in 1914- was supposedly gathered by the Persian king Xerxes in Asia Minor in 481 BC. The individual contingents from the most distant parts of the empire already had up to 4,000 km behind them when they arrived and had to march for more than half a year. And this mighty army was then in the spring of 480 lead 1,200 km further from there across the Hellespont through Thrace and Thessaly before they finally confronted the enemy. The length of the march column of this army with baggage train, marching along a single street, must have amounted to at least 4,000 km (the great circle distance from Lisbon to Moscow) and the march from the rear of the column to the front must have required seven months’ time! Was there in Xerxes’ army a logistical wizard, who could feed such masses without railroads; was there a Moses, who could supply such gigantic masses of humanity and animals with water? Or did the Persian have aircraft and wireless telegraphs for the transmission of messages, commands and miscellaneous communications of the commanders across thousands of kilometers? If the great general Napoleon lead only 450,000 men into Russia in 1812, well-organized, disciplined, exercised troops with professionalized, experienced officers and staffs, and certainly not on a single street, but along many roads over a breadth of several hundred kilometers, nevertheless his plans shattered on the very same distances and difficulties of supply!

Indeed armies of 200,000-300,000 men operated in Germany, Austria, and France without modern means of transportation in the time of Napoleon I. But these were the well organized, disciplined, well trained troops under professional leadership, and, what should be especially emphasized, they marched in separated march columns of moderate strength through intensely cultivated, wealthy districts cut with numerous streets, in which they could live to a good part from the produce of the land, and therefore also, aside from greater frugality, could satisfy themselves with a much smaller baggage train (Troß), while a union of larger bodies of troops for the battle took only a few days.

Its true that Herodotus says (9.28) that the free Greeks eventually gathered an army of almost 40,000 hoplites to face the Persians at Plataia. But that was after the Persians had already suffered some setbacks, and when they were planning their invasion the King’s Men were probably expecting to fight a coalition of a few cities the size of Sparta and Athens, with 6,000 to 10,000 hoplites each, plus a handful of smaller cities with a thousand or two hoplites each. Thucydides insists that the battle of Mantinea, with about 10,000 hoplites on each side, was the greatest battle between Greeks “for a long time” (5.74.1). An army of 40,000 or so soldiers, minus losses and plus local allies like the Thessalians and Thebans, should have been enough for people who hadn’t read Herodotus and learned that one Greek was worth three barbarians.

At the end of his article von Fischer turns to the problem of how Herodotus could repeat such an absurd idea:

Contemporaries of the events also lacked the understanding and above all a measure for estimating troop strengths. People who had never yet seen large bodies of troops in different formations overestimated correspondingly their numbers very significantly, especially in the case of long march columns with baggage train (Troß). In times of excitement such overestimates multiplied. So one can assume that from the beginning such excessive numbers spread from mouth to mouth in Greece, were further increased and confused in the excitement of wartime and probably also for the increase of the fame of their fellow-countrymen, until they finally arrived over the whole generation between the war and the investigations of Herodotus, who in addition was more than uncritical about measures and numbers and had no precise understanding of military matters.

After all, the largest battles we hear about in archaic Greece involve a few thousand hoplites on each side, and its likely that the typical Greek battle before the Persian wars took place when an aristocrat lead a few hundred friends and hangers-on up a beach or over the hills to steal some cattle and slaves and tripods. And von Fischer could have mentioned that Xenophon and Thucydides and Diodorus describe how easy it was to overestimate the size of an army which marched slowly two abreast, made more shelters or campfires than expected, or whose market mob was unable to get away before the fighting and took shelter behind the soldiers screaming and throwing things. His rule of thumb of no more than 45,000 heads along a single road is pretty close to figures for large but not gigantic Macedonian and Roman armies which seem to have all come into the same camp in a single night.

Without Persian documents, we can’t know the size of the army that invaded Greece in 480. But its important to remember that the idea that the invasion of Greece was an overwhelmingly important event, or that eastern armies were especially large, is only found in classical literary sources. No Babylonian or Assyrian king claims to lead more than 120,000 men (and I don’t know anyone who thinks that that number is based on a count). And in all of world history, I can’t find solid evidence for an army of 100,000 120,000 or more men before the Napoleonic Wars. And while an invasion of tens of thousands of soldiers from beyond the sea was the biggest thing which had ever happened in Attica, for the Persians it was Tuesday. Everyone from Aristophanes to Thucydides to Theopompus said that the Athenians loved to talk up what they had done against the Persians, and there are people today who think that the Spartan reputation as tough guys was born at Thermopylae.

As a general rule, British critics tend to try to save as much of Herodotus as they can, while Germans and Austrians are franker that he or his sources could just have made things up. Where British commentators often rely on common sense and look very closely at ancient texts, Germans apply reason and general principles. So I think that its characteristic that where Maurice calculated the largest force which he could imagine leading through the area, von Fischer thought about it and gave the size of army which would be most practical.

I thank Ursula Weber for citing this article in Das Reich der Achaimeniden: Eine Bibliografie (1996).

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Further Reading:

  • Maurice, F. (Frederick Barton) (1930) “The Size of the Army of Xerxes in the Invasion of Greece, 480 B.C.” Journal of Hellenic Studies 50 pp. 210-235
  • von Fischer, Robert (1932) “Das Zahlenproblem im Perserkriege 480-479 v. Chr.” Klio 25 = N.F. 7 pp. 289-333 link
  • Lee, John W. I. (2008) A Greek Army on the March: Soldiers and Survival in Xenophon’s Anabasis (Cambridge University Press: Cambridge)
  • Roth, Jonathan P. (2012) The Logistics of the Roman Army at War (264 BC – AD 235). Brill: Leiden.

16 thoughts on “The Number Problem in the Persian Wars 480-479 BCE

  1. russell1200 says:

    Doesn’t the Persian Navy bouncing along the coast with the army somewhat muddy the picture? It seems like after 4 years of preparation the Persian might have had some clever logistics planned out.

    That wouldn’t mean 4 million troops, but it certainly could be a very large number.

    1. Sean Manning says:

      Well, first off, they didn’t just march along the coast! The army assembled at Critalla in Cappadocia, marched all the way to Sardis inland, and spent a whole winter there. They spent the next winter in Thessaly, not exactly the easiest part of Greece to access by sea even if they had not sent away their fleet.

      And second, the basic issues with roads are still the same even if someone has already stockpiked food at both ends of the road (and the fleet creates its own issues: those rowers need food and water and fuel too and now you have to synchronize a fleet at the mercy of harbours and wind and currents and a land army driven by feet and grass). Even if you assume a fleet of 300 Athenian-style triremes (and Herodotus says that they had more men on board), that is another 60,000 men who all need to eat and sleep and poop.

      Just getting an army of 20,000 or 40,000 or 80,000 men together and keeping them together was an extraordinary achievement, and I can’t find any solid evidence for much larger armies anywhere in world history before 1789 (lots of chroniclers with round numbers in the hundreds of thousands for armies long ago and far away, never the kind of thing J.F. Verbruggen would give a second look at). If you check out the dissertation, I have two case studies of numbers estimated by foreigners vs. numbers in internal documents in the Ottoman Empire and the Second World War, plus another on numbers in chroniclers vs. numbers in documents at Agincourt.

      1. Dariusz Wielec says:

        interesting blog –
        re your observation on the numerical strength of the pre 1789 armies:

        -”Just getting an army of 20,000 or 40,000 or 80,000 men together and keeping them together was an extraordinary achievement, I can’t find any solid evidence for much larger armies anywhere in world history before 1789”-

        well, in our neck of the woods – i.e. the Central & Eastern Europe the early modern period saw huge armies especially during the 17th century. And there are primary sources to support the numbers.
        eg – three examples involving the 17th century Polish armies:

        battle or rather the siege of Polish army at their fortified camp at Khotyn 1621(Ukraine today) – Polish-Lithuanian army about 45-50 thousand strong (professional soldiers and Zaporozhian Cossacks) commanded by hetman Chodkiewicz versus the Ottoman army under the sultan of about 120-140 thousand soldiers plus camp servants (perhaps as many as 100 thousand). Lasted for about 5 weeks .

        AD 1651- at the battle of Beresteczko (Berestechko, present day Ukraine) the Polish-Lithuanian army was about 80 thousand soldiers(professional and national levy) plus perhaps as many as 100 thousand servants (who at times fought too) commanded by king Jan Kazimierz.
        The opposing side consisted of the Ukrainian rebels – about 100 thousand Zaporozhian Cossacks & Ruthenian peasants and burghers commanded by Khmielnicki, and their allies: about 30 to 50 thousand mounted Tatars (Crimean and their vassals) commanded by the khan.
        Vast numbers of horses – perhaps as many as 300,000 – the Tatars had at least two horses per warrior, and the elite as many as 10, while the Polish and Cossack wagons were pulled by the 2-horse teams, Polish national cavalry had at least 2 to 5 horses per cavalryman. Polish national levy alone brought some 80 thousand wagons to the battle.
        The battle took 3 days to decide, and then 10 days to break-in and capture the wagonburg of the Zaporozhian Cossacks).

        During the battle of Vienna AD 1683 fought on 12th of September, the Christians’ allied command under the Polish king Jan III Sobieski consisted of about 70 thousand of soldiers (plus the servants – unknown number) while the vizier Kara Mustapha’s Ottoman side had almost 130 thousand of soldiers plus unknown number of camp servants (perhaps as many as or equal to the number of soldiers). The Ottomans had many more soldiers (160 thousand) but they deserted, died or got sick or were taken away during the preceding months of marching and siege.

        and there are other battles where numbers were rather respectable.

        1. Sean Manning says:

          Hi Dariusz, my most important question is simple: what is the source? In my PhD thesis I use Rhoads Murphy’s research, where the largest army any Ottoman writer claims to have is 73,589 cavalry and 35,000 infantry at the siege of Baghdad in 1638 and archival documents suggest that this number was on the high side, and Zamulin’s research on the battle of Prokharovka in 1943 which probably involved 978 not 1200 or 1500 armoured fighting vehicles (but Soviet official historians give the higher figures because it was a great patriotic victory and because early on one of them made an arithmetic error).

          Back in the 1950s, medievalists like J.F. Verbruggen more or less gave up on using numbers in stories about battles to understand the size of the armies involved, and switched to focus on archival documents. Anne Curry is a forceful advocate of this view today.

          We find all kinds of stories about vast armies all over world history, but when we have archival records they shrink back down to 100,000 soldiers or less until roughly the Napoleonic Wars. (And its very important to compare likes with like: counts of soldiers to counts of soldiers, not counts of soldiers + camp followers).

      2. Radosław Sikora says:

        “And its very important to compare likes with like: counts of soldiers to counts of soldiers, not counts of soldiers + camp followers”

        Could you define “soldiers”, please?

        1. Sean Manning says:

          Hi Radoslaw, that is a complicated topic but see the relevant sections of my MA thesis and my PhD thesis.

          In practice, its usually clear when someone is including just the paid, armed soldiers in one army but every warm body in the other army, often using completely arbitrary numbers for the camp followers because none of their sources counts them (in my MA thesis, I give an evidence-based way to estimate how many camp followers there were). When someone is so kind as to commit such a beautiful logical fallacy, they deliver themselves into their debate partner’s hands.

      3. Radosław Sikora says:

        „that is a complicated topic but see the relevant sections of my MA thesis and my PhD thesis.”

        Thank you. I’ve read it. Unfortunately I am not able to find a definition of a „soldier”. The definition is a key problem, because depending on a time and an army, some categories of „men in army” once are counted to soldiers but another once they are not. So your postulate („And its very important to compare likes with like: counts of soldiers to counts of soldiers, not counts of soldiers + camp followers”) is logic, but in practice it is impossible to honest use. Personally I prefer to use a term ‘armed men’, because it is wide enough to include all kinds of soldiers in all epochs. So talking about numbers we should talk about ‘armed men’ in armies.

        1. Sean Manning says:

          Yes, I don’t think an abstract definition of ‘soldier’ is useful. We have to work with the sources we have, and those sources count whichever types of people were important to them not the type we want them to count or the type another culture counted. But we can make sure we are comparing like to like, and we can keep our eyes on the light of the terrible truth: from the Bronze Age to 1800, it is very hard to find strong evidence for an army, as in a group of troops in one place at one time, with much more than 100,000 soldiers plus their camp followers.

          I don’t know of any cases where quibbling about the definition of “soldier” and “non-combatant,” like Will McLean’s disagreement with Anne Curry whether gros valets/haubergeons/coustiliers are soldiers in the Hundred Years’ War, would change this fact.

          The way this game works is that when people feel that the part of an army which they can count or estimate has an unimpressive number, they start multiplying it and talking about horses or camels or washerwomen or bakers or bushels of barley or baskets of horse-dung. Those kinds of calculations are fun, but they can never be more accurate than the numbers which went into them, which are usually numbers of soldiers. Or they confuse the number of men liable for military service, the number in service somewhere in a vast empire in a given month, and the number within a 10-mile radius on a given day.

      4. Radosław Sikora says:

        „Yes, I don’t think an abstract definition of ‘soldier’ is useful. We have to work with the sources we have, and those sources count whichever types of people were important to them not the type we want them to count or the type another culture counted.”

        And it has a fatal consequences. I’ll give you an example. You write:

        “we can keep our eyes on the light of the terrible truth: from the Bronze Age to 1800, it is very hard to find strong evidence for an army, as in a group of troops in one place at one time, with much more than 100,000 soldiers plus their camp followers”

        Call these camp followers (armed men, who from time to time participated in fights, although their ordinary duty was logistic etc.) “soldiers” and you will suddenly discover that 16-17th c. armies sometimes had even hundreds of thousands of soldiers. Such numerous armies were able to march hundreds of km, feed itself and fight.
        Don’t call people (now called “soldiers”) responsible for logistic and another non-combat tasks “soldiers”, and you will suddenly discover that moder armies are much smaller. For example look at air forces. Pilots are only a small percent of the whole forces. The rest of soldiers have similar duties to camp followers in the past. They are necessary to combat capability of pilots, but they don’t fight (contrary to camp followers in the past, who were fighting from time to time with weapons in hands).
        As you can see, all depends on a definition of soldiers. Depending on the definition your conclusions might be true or false.

        1. Sean Manning says:

          If you chose, you can estimate the number of men or bodies in an army. As a rule we don’t have sources for those before the 19th century so you have to speculate and calculate based on numbers of soldiers. But then to compare your results with Herodotus’ claim that there were 1,800,000 soldiers (plus uncounted servants, women, and eunuchs) in Xerxes’ army, or other writers’ figures for the number of soldiers in various Greek, Macedonian, Roman, Byzantine, and Ottoman armies, you have to work back from that total of bodies to a total of soldiers. Evidence for an army of 200,000 human beings is not evidence for an army of 200,000 soldiers plus washerwomen and bakers and sutlers, any more than evidence that Augustus had 30 legions is evidence he could deploy 30 legions to Spain or Armenia.

          As it happens, the armies von Fischer was familiar with had a ratio of soldiers to noncombatants which is pretty close to our best guess for efficient Greek and Roman armies (and his understanding of the difference was pretty similar to ancient understandings, although he did not forget to count low-status infantry like Herodotus, Thucydides, and Xenophon sometimes forget). Armies with more noncombatants would be able to fit fewer soldiers through the same road network and feed fewer soldiers from the same grainaries.

          As people realize that they can’t provide good evidence that one kind of number could be as high as they want, they start talking about another type of number which could be bigger, but that does not affect the original discussion. That is why I am so insistent that someone who believes in armies of hundreds of thousands of soldiers, plus noncombatants, provide strong evidence that such armies existed somewhere before the 18th century. Once we are talking about specific cases and specific evidence, we can have a useful discussion about issues like whether to count servants in classical Greek armies, all those robbers with a horse and some kind of weapon at Assaye, or the reliability of specific sources.

    2. Sean Manning says:

      Also, if you look at very big armies where we have some detailed sources, like the two sides at Actium, the sources usually talk about supply by sea or down a navigable river. So when Hellenistic and Roman and Byzantine and Ottoman armies reach limits somewhere in neighbourhood of 80,000 to 120,000 soldiers, those are the limits using all the available resources.

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  4. Peter Thomson says:

    I found Engels’ Logistics of the Macedonian Army convincing, given that the available ancient evidence was matched against field observations by people thinking in terms of water and forage for a foot-and-horse based army. These support your observation that 100,000 is probably the absolute maximum for such army – and most were certainly much smaller.

    Just in terms of marching and camping, 10,000 (the size of a Napoleonic division, a Mongol tumen and a Roman legion plus auxiliaries) seems close the usual practical size for a unit that can use a single road, negotiate a defile in a day and access water in a reasonable time.

    1. Sean Manning says:

      The only reasons why I don’t have Engels in the recommended reading are that he believed a myth about ancient carts and wagons, and he assumed that Achaemenid Iran was just like Qajar Iran when we now know it was more agrarian (less nomadic), more forested (less barren rocks), and had a more developed system for collecting and redistributing produce. But his book is definitely more digestable than Jonathan Roth’s and it is affordable too.

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