Mardonius was a prominent Persian noble and general of the Achaemenid Empire, closely connected to the royal family through marriage. He first appears in the sources as a commander tasked with reasserting Persian control over Ionia and preparing the way for an invasion of mainland Greece.
After the failures of Darius I, Mardonius strongly encouraged Xerxes I to renew the war against the Greek city-states, arguing that a decisive victory would secure Persian prestige and remove a troublesome frontier. He played a key role in planning the massive invasion of 480 BC.
When the Persian navy was shattered at Salamis and Xerxes withdrew to Asia, Mardonius remained in Greece with an elite land force. He tried both carrot and stickโoffering favorable terms to Athens while also ravaging the countryside when negotiations failed.
In 479 BC, he met the largest Greek army yet assembled at Plataea. Despite his numerical strength, Persian cavalry advantages and early successes could not break the disciplined hoplite phalanxes. During the fierce fighting, Mardonius was killed, and his army collapsed, marking the effective end of the Persian invasion of mainland Greece.