Final answer:
The alliance of Greek city-states, known as the Hellenic League, promised to protect its members against the Persian Empire, forming mainly to resist invasions such as the one led by Persian King Xerxes around 480 BCE. The Delian League was another such alliance, created after the Persian Wars to continue resisting Persian interference and protect Greek independence.
Step-by-step explanation:
This alliance of Greeks promised to protect its members against the Persian Empire.
The Greeks, particularly the city-states or poleis, faced significant threats from powerful external forces such as the Persians and later, the Macedonians. During the period around 480 BCE, most Greek city-states united to form the Hellenic League to defend against the Persian invasion led by King Xerxes. This league was a remarkable act of unity given that Greek daily life was typically centered around loyalty to one's individual city-state. Sparta took the lead in commanding the armies, while Athens controlled the naval forces.
In another instance, the Delian League was established after the Persian Wars, primarily led by Athens around 477 BCE, to continue the fight against Persia and to assure the freedom of Greek city-states. Instead of direct military support, member states often contributed funds to maintain a powerful fleet to deter further Persian interference. Over time, Athens used this league to augment its own power, controlling the contributions of other cities and solidifying its dominance in the Greek world. The leagues were a testament to how the Greek poleis could set aside their independence for collective security when facing a common threat.