The Battle of Thermopylae and the heroic fight of Leonidas and the 300 Spartans (as well as several thousands of other Greeks who are usually forgotten) against a numerically far superior enemy is one of the most famous battles of history and inspires people until this day.
But while everybody agrees that the Persian numbers were far greater than the Greek numbers, the exact number of Persian warriors in the Battle of Thermopylae is usually overexaggerated. So in this article, I will present how many Persian soldiers were really fighting at the Battle of Thermopylae.
The Greek writer Herodotus claims that the Persian army that invaded Greece in 480 BC and fought in the Battle of Thermopylae in August of 480 BC was comprised of 2,7 Million soldiers. But that number is way too high. 100,000 Persian soldiers (including 10,000 elite Immortals and 10,000-15,000 cavalrymen) is much more realistic and would`ve still been a giant threat (Alexander the Great only had 32,000-47,000 men when he conquered the Persian Empire).
But the size of Alexander the Great`s army is a story for another time.
Let`s now look at why Herodotus claims such an unrealistically high number of Persian soldiers. And then we will look at how many Persian soldiers were really fighting at the Battle of Thermopylae.
The Size of the Persian Army According to Herodotus
One of our most important written sources for the Greco-Persian Wars is „The Histories“*, written by Herodotus. These books are really interesting! So if you want to read about the Greco-Persian Wars from the eyes of an ancient Greek who lives about 1 or 2 generations after the warsI can highly recommend you the book. You can find a translated version here* on Amazon.
The ancient Greek writer Herodotus claims that the Persian army consisted of 1,7 million infantrymen, 300,000 warriors from the European & Greek allies of the Persian Empire, 80,000 Asian cavalrymen as well as a total of 20,000 Lybian & Indian chariot warriors and Arabian Camelriders.
Having said that, while the Histories are a great book they also have to be taken with a huge grain of salt, especially when it comes to numbers.
Why did Herodotus Exaggerate the Number of Persian Soldiers?
The reason for that can be found in the reason why Herodotus wrote „The Histories“ in the first place. I wrote an entire article on that topic, so I will only sum it up now. But if you want to find out about Herodotus` motivations for writing „The Histories“ you can check out my article here.
The main goal of Herodotus was to entertain the reader of his book „The Histories“, not so much to report the actual events (the same can be said for many other ancient writers). So speeches, battle tactics, but also army sizes are often added or altered to improve the reading pleasure. Additionally, Herodotus also competed with Homer and his book about the Trojan War („The Iliad“) over who reported about the greater and more significant war.
The Iliad* is also one of these books that I can highly recommend! But since the Trojan War – unlike the Greco-Persian Wars – was a series of tales and myths, Herodotus basically had to increase the actual size of the Persian army to prove that he was indeed also writing about an important war.
All of that has to be remembered when we read in „The Histories“ of Herodotus that the Persian army consisted of 2,7 Million soldiers.
But that obviously bears one question: How do we know that the numbers that Herodotus gives us are overexaggerated?
Why the Number of Persian Soldiers Reported by Herodotus is unrealistic
Ok, so Herodotus gives us the number of 2,7 million Persian soldiers. But that seems highly unrealistic (just for comparison, Hitler invaded the Soviet Union with 3,5 million soldiers in 1941).
Supplying an army of 2,3 million men in the 5th century BC was simply impossible. And when we take the average width of the Persian marching columns into regard, then the first of the 2,3 million Persian soldiers would have arrived at the Thermopylae while the last would have just left the city of Babylon in Iraq. So it becomes clear that the size of the Persian army that Herodotus gives us can`t be true.
Ok, so that leaves one question:
How many Persian soldiers were really invading Greece and fighting at the Battle of Thermopylae?
How Many Persians were fighting in the Battle of Thermopylae?
Historians don`t know the exact size of the Persian army that invaded Greece. But most estimations range around the number of 100,000 men. Now that might sound not that impressive compared to the 2,7 million soldiers Herodotus claims.
But when we compare that to the usual army sizes of ancient Greece, then it turns out that 100,000 men were an enormous army and a giant threat! I mean let`s face it, Alexander the Great only had 32,000-47,000 men when he successfully invaded the Persian Empire!
It seems likely that the Persian army that invaded Greece in 480 BC and fought at the Battle of Thermopylae in August of 480 BC consisted of up to 100,000 soldiers (including 10,000 elite Immortals and 10,000-15,000 cavalrymen) plus an unknown number of Macedonian and Thracian allies.
Needless to say that an army of such size was a giant threat, especially when we consider that – unlike many think – not all of Greece united against Persia. Quite the opposite is true. Only a small minority of Greek city-states joined the Hellenic League to fight the Persian invasion, more on that here.
Ok, there we have it. The size of the Persian army.
Do you want to find out more about why the Greeks fought at the passage of Thermopylae despite knowing perfectly well that they would not be able to defeat the Persians? Then I would like to recommend you my article here where I talk about the Greek plan in great detail.
Take care of yourself because you deserve it. You really do.
Until next time
Yours truly
Luke Reitzer
Sources
Homer: The Iliad.* https://amzn.to/3L24ouW
Karl-Wilhelm Welweit: Sparta. Aufstieg und Niedergang einer antiken Großmacht (Stuttgart 2004).*
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