The Greco-Persian Wars, also known as the Persian Wars, were a series of wars between Ancient Greek states and the Achaemenid Empire, which made several attempts to conquer the Ancient Greek states, but was defeated, despite the Achaemenid Empire having vastly greater resources.
Notable battles include Marathon, Thermopylae, Salamis, and Plataea.
The wars are often described as occurring between 492–449 BC. However, there were various later conflicts, with the Achaemenid Empire rather successfully inciting internal Ancient Greek conflicts and participating in the internecine wars.
Xenophon and other Greeks participated in a civil war in the Achaemenid Empire, again achieving military successes, despite being greatly outnumbered.
Finally, Alexander the Great conquered the Achaemenid Empire.