In the fall of 480 BC, Xerxes, avenging his fathers loss to the greeks at Marathon, invaded the greek peninsula again. Various political factors left the city-states unable to field their main armies in a timely manner, so Leonidas, one of two Spartan Kings, took his personal guard of 300 men, their supply train, and in conjunction with some other forces, arrived at, and began fortifying the narrow pass between the cliffs and the sea. Roughly 7000 men faced an army often described in the million…