The Persian Invasions refer to a series of military campaigns launched by the Achaemenid Empire against the Greek city-states during the 5th century BCE. The most notable invasions occurred under the rule of Darius I and his successor, Xerxes I. These invasions aimed to expand Persian territory and assert dominance over Greece. The first major invasion began in 490 BCE with the Battle of Marathon, where the Persians faced a surprising defeat. The second invasion in 480 BCE included significant battles such as the Battle of Thermopylae and the Battle of Salamis, ultimately leading to Persian withdrawal and the preservation of Greek independence.