The Persian army had failed in their attempt to overthrow Greece during the 1st Persian Invasion of 490BC, however they were not to be deterred.
Persia was now led by King Xerxes I following his father King Darius I death, and Xerxes was determined to conquer all of Greece. He was to spend many years planning this and the invasion lasted 480BC – 479BC.
The Battle of Thermopylae took place in 480BC and was to last 3 days.
King Xerxes I set out to conquer Greece and he marched his army towards Thermopylae. There is dispute about the size of his army, but it could have been 100,000 – 150,000 strong.
An alliance of Greek city-states had amassed 7,000 men led by King Leonides of Sparta and in the summer of 480BC they marched north to block the Persian army at the mountain pass at Thermopylae.
Xerxes and his army arrived in late August, but did not to attack the Greeks; he waited 4 days thinking the Greeks would flee as they were so heavily outnumbered. This was not to be the case.
On the 5th day the Persian army attacked. Xerxes ordered 5,000 archers to fire arrows directly at the Greeks, but these were highly ineffective against the shields of the Greek army. He then followed this with 10,000 men sent in a full frontal attack.
The Greeks held their position in the Phalanx (shoulder to shoulder) position. Although outnumbered they were better armoured with their long spears, swords and shields.
Many Persians were killed in this attack with only small losses to the Greeks.
The Persians attacked again with another 10,000 men, running straight at the Greek army who then pretended to retreat. They then turned back and slaughtered the Persians as they were running towards them.
The following day Xerxes attacked again with his infantry, but he could still not break the Greek lines. He then retreated back to camp with his men.
The Greeks were to be betrayed by one of their own. A native Greek named Ephialtes , hoping for a reward betrayed the Greeks and told Xerxes of a mountain pass around Thermopylae. He offered to guide the Persians through it.
On the evening of the 2nd day of battle Xerxes ordered his Commander Hydarnes to take 20,000 men and circle the pass of Thermopylae.
At dawn on the third day the Phocians (Greeks) who were guarding the path above Thermopylae, became aware of Persians approaching. They armed themselves, but the Persians were not interested in fighting them and merely shot arrows at them as they passed. They continued marching towards their goal, the main Greek force, which they then encircled.
Leonidas was told of the Persian advance and held a council of war.
Following this only 1,500 men were to stay and fight. Many were either ordered to go or chose to leave.
Xerxes with his infantry and cavalry charged at the Greeks and they met head-on at the widest part of the pass. The Greeks fought bravely and in the ensuing battle their leader the Spartan King Leonidas was to die. His comrades were determined to recover his body and they fought fiercely to do this.
The Greeks fought bravely to the end, even continuing to fight with just their hands, but it was a hopeless cause and the Persians were victorious.
The mountain pass was now open to the Persians to continue with their quest to conquer all of Greece.