Indicate the name of the battle during which 300 Spartans led by tsar Leonidas performed their feat.

We are talking about the Battle of Thermopylae, which took place in September 480 BC.

This battle took place during the Greco-Persian War. The invading army of the Persian king Xerxes was huge for that time. The Spartan king Leonidas with auxiliary troops from other Greek places stood in the way of the advance of the Persians.

The battle unfolded in the Thermopylae Gorge, where the larger Persian army could not flank and encircle the smaller forces of the Greeks.