Final answer:
The Persian War started as a result of the Greeks assisting in the Ionian Rebellion against Persian rule, after which Darius of Persia sought to punish Athens and other allies for their intervention.
Step-by-step explanation:
The conflict that began as a result of the Greeks assisting in a rebellion was the Persian War. The Ionian Rebellion in 499 BCE saw several Greek city-states from Ionia, under Persian control, rise against Persian rule. Athens and other Greek allies supported the Ionians, which angered King Darius of Persia, ultimately resulting in a series of invasions that are collectively known as the Persian Wars. This struggle happened as a reaction to the Ionian Greeks' resistance against the Persian Empire's hold on their region and the subsequent intervention by mainland Greece, particularly Athens.
It's noteworthy that assisting the rebellion had significant long-term consequences, eventually leading to hard-fought Greek victories like the Battle of Plataea in 479 BCE. Following their success, the Greeks, especially Athens, continued resistance against Persian rule, leading to the eventual peace settlement around 449 BCE that acknowledged the independence of the Greek city-states in Ionia.