One of the most remarkable actions in military history took place at Thermopylae in 480 BC. Rupert Matthews has personally examined the battlefield in order to try to explain how 300 Spartans could hold at bay the hordes of the Persian Emperor Xerxes. The Spartan battle was no vain sacrifice; the delay gave breathing space for the Greek states to organize their defense, and ultimately to successfully defend their homelands. This study explains the importance of the half-ruined wall that sheltered the Spartans against the onslaught, and uncovers other little-known facts. Concise diagrams and maps of the entire campaign illustrated the extraordinary and seemingly impossible outcome of the war.