Part 2/12:
The seeds of conflict were sowed by Xerxes I, the ruler of the vast Achaemenid Empire, who sought revenge for his father Darius I's humiliating defeat at the Battle of Marathon. Preparing for a massive invasion that culminated in 480 BC, Xerxes amassed an army of potentially 100,000 to 300,000 soldiers, establishing extensive supply lines and even constructing a pontoon bridge over the Hellespont.
As Xerxes' forces marched through Thessaly and Macedon, local leaders faced a daunting choice: join the Persian empires or be crushed. However, the fragmented Greek city-states, often at odds with one another, finally united under Spartan and Athenian leadership. The Greeks aimed to block Xerxes at two crucial chokepoints: the narrow pass of Thermopylae and the strait of Artemisium.