Legend of the Three Hundred is about the battle of Thermopylae where famously 300 Spartan hoplites resisted against the military advances of the Persian Empire (headed by Xerxes) in the 5th century B.C. It is to note that there were more troops fighting on the Greek side during the battle than just the 300 Spartans. Another fact to be stated is that there were more Greeks fighting for the Persian army than for all the Greeks. While according to modern estimates there were only 300,000 Persian troops at the battle, The Histories by Herodotus give a number of 3 million which is how large the Ancient Greeks perceived the Persian Army to be.