Final answer:
Greek city-states formed the Hellenic League, with Sparta leading the land forces and Athens the naval forces, to defend against Persian attacks by Xerxes. Strategic defenses like Thermopylae and the naval Battle of Salamis led to the Persian withdrawal and eventual Greek victories.
Step-by-step explanation:
In response to the constant threat of Persian attacks by Xerxes, many Greek city-states joined together in a Hellenic League, an alliance aimed at defending themselves against the invading forces.
Under the leadership of Athens and Sparta, the Greek city-states united to face the Persian threat.
The Spartans, known for their military prowess, took command of the land army, while the Athenians, with their burgeoning naval strength, led the fleets.
The defense strategy involved holding off the Persians at strategic points such as Thermopylae, where a small force led by King Leonidas of Sparta famously resisted the massive Persian army.
The Athenians, meanwhile, concentrated on naval engagements like the decisive Battle of Salamis, where the Greek fleet scored a significant victory against the Persian navy.
The success of these combined defenses culminated in the withdrawal of Xerxes' forces and eventually led to the defeat of the Persians in Greece, particularly at the battle of Plataea and subsequent liberation efforts of Greek city-states in Ionia and beyond.