300 in History

from Wikipedia:

In the Battle of Thermopylae of 480 BC, an alliance of Greek city-states fought the invading Persian Empire at the pass of Thermopylae in central Greece. Vastly outnumbered, the Greeks held back the Persians for three days in one of history's most famous last stands. A small force led by King Leonidas of Sparta blocked the only road through which the massive army of Xerxes I could pass.

After three days of battle, a local resident named Ephialtes betrayed the Greeks by revealing a mountain path that led behind the Greek lines. Dismissing the rest of the army, King Leonidas stayed behind with 300 Spartans and 700 Thespian volunteers. The Persians succeeded in taking the pass but sustained heavy losses, extremely disproportionate to those of the Greeks.

The fierce resistance of the Spartan-led army offered Athens the invaluable time to prepare for a decisive naval battle that would come to determine the outcome of the war.[4] The subsequent Greek victory at the Battle of Salamis left much of the Persian Empire's navy destroyed and Xerxes I was forced to retreat back to Asia, leaving his army in Greece under Mardonius, who was to meet the Greeks in battle one last time. The Spartans assembled at full strength and led a pan-Greek army that defeated the Persians decisively at the Battle of Plataea, ending the Greco-Persian War and with it the expansion of the Persian Empire into Western Europe. [5]

The performance of the defenders at the battle of Thermopylae is often used as an example of the advantages of training, equipment, and good use of terrain to maximize an army's potential,[6] and has become a symbol of courage against overwhelming odds.[6] The sacrifice of the Spartans and the Thespians has captured the minds of many throughout the ages has given birth to many cultural references as a result.[7]