Battle of Thermopylae

According to Herodotus, the army led by Xerxes numbered five million two hundred and eighty-three thousand men – including a battle-worthy two million six hundred and forty thousand.

An excerpt from the article 31 facts about Battle of Thermopylae

Such a large throng of people (as well as accompanying animals), even under today’s conditions, would be a logistically impossible task. Therefore, modern historians estimate the size of Xerxes’ army at 120.000-300.000 armed men (some allow the figure of 500.00). The army included soldiers of various nationalities-Assyrians, Phoenicians, Babylonians, and Indians. Egyptians, Jews, Arabs, and others. At least 10.000 of them were so-called “Immortal”-elite warriors who were also royal guards. Led by Xerxes, the fleet included 1207 triers (ships equipped with sails and three rows of oars) and 3000 transport ships. The army also had heavy cavalry and battle wagons.