Final answer:
The Spartans inspired the Greeks with their heroic but ill-fated defense against the Persian army at the mountain pass of Thermopylae in 480 BCE.
Step-by-step explanation:
In 480 BCE, the Spartans displayed a legendary defense against the Persian army at the mountain pass of Thermopylae. King Leonidas and his Spartan warriors delayed the massive Persian forces under Xerxes I, despite being vastly outnumbered. This act of bravery provided crucial time for the Greek city-states to organize their defenses, culminating in further engagements such as the naval Battle of Salamis where the Greeks triumphed. Although the Spartans were ultimately defeated after being betrayed, their sacrifice had a significant impact, uplifting the spirit of the Greek allies and securing unity within the Hellenic League.