Leonidas I of the Agiad dynasty was one of the two kings of the ancient Sparta during the years immediately leading up to the ‘Second Persian War’. The 17th ruler of his line, he was the commander of the 7000 allied Greek forces (modern estimates) against the invading Persian army of 300,000 (modern estimates) at the ‘Battle of Thermopylae’. While the future kings of Sparta were generally exempt from the agoge, the rigorous education and martial training program that all male citizens of the city were subjected to, Leonidas underwent it just the same, not being the initial successor to his father’s throne. He became the co-king of Sparta at around the age of fifty. Nine years into his reign, Greece was attacked by the Persian emperor Xerxes I as a delayed response to the defeat in the ‘First Persian War’ in 490 BC. A military alliance known as the ‘Corinthian League’ was forged under the Spartan leadership among the warring city-states and it was decided that Sparta would lead the defence of the narrow pass of Thermopylae that linked Persia-controlled Thessaly to the central Greece. In the ensuing three-day battle, every soldier of the Greek army except for the 400 Thebans who surrendered to King Xerxes was killed. Leonidas and his martyred warriors have become the symbol of patriotism and sacrifice since then and their battle tactics the matters of discourse in military schools.