Part 3 tells the story of how Sparta became the single most dominant power in Greece, and how it then lost it all. After the Spartans take the war to Syracuse (Sicily), some major on-field and off-field victories were won over the Athenians, and Sparta eventually defeated it's mighty navy. Sparta blockaded Athens, invaded it, and then subjugated it. Sparta then seemed to loose it's focus, became corrupt and decadent, and a sharp decline in fortunes began. Along with the widespread corruption, a decline in the overall numbers of actual Spartan citizens - due to deaths in it's many wars, along with it's very rigid class system, which included a program of infanticide - brought about the decline in Sparta's fortunes, leading to war with Thebes. In 371 BC, the battle of Leuctra finally saw the end of Spartan dominance in Greece.