The battle was fought around August 7th or September 8th, in the year of 490 B.C. It was fought by the alliance of the Greek city-states under the power of King Leonidas of the Spartans and the Persian Empire Xerxes.
A force of 7,300 Greek men marched to guard the passage of Thermopylae. King Leonidas heard that a force of Persian troops were marching to take the passage, which was vital to the Greeks. The passage was an entrance into the city of Athens. Thermopylae was a narrow pass. To one side were rocky mountains and to the other was water.
After the Greek forces, killed by the 300 Spartans, arrived they began to assemble into ranks. It was to my belief, and the belief of some historians, that the higher ranks were in the front. After assembled the Greeks saw some horsemen riding over the mountains. An attack by horsemen was a good idea, but not over the rocky mountains because it would take too long and the Greeks would have been well prepared. An attack by horsemen would have been better by going through the passage.
The attack would have been better if they had used horseback archers. The archers could have fired from a distance and had a better chance of having a successful attack. The horsemen were easily defeated. After the horsemen were defeated an army of 10,000 Persian soldiers marched towards the 7,300 Greek soldiers.
The Persians had the biggest land force in the world at that time. Part of their army was called the immortals because when one man died or retired he was replaced at the same time so that their numbers stayed the same. The Persians had cloth wrapped around their head so that they could see you while you couldn't see them. Their armor had a cool design, but it was only as thick as a playing card. Their shields were wicker. The shields could withstand arrows and daggers, but they were no match for the Greek spears.
On the other hand you had...