Mardonius (märdōˈnēəs) [key], d. 479 B.C., Persian general; son-in-law of Darius I. Darius sent him (492 B.C.) to retaliate against Eretria and Athens for aiding the Ionians in the Persian Wars, but his fleet was lost in a storm off Mt. Athos, and a Thracian tribe destroyed a large part of his army. He helped Xerxes I plan his invasion of Greece. Xerxes returned (480 B.C.) to Persia after his defeat at Salamis and left Mardonius in command in Greece. Mardonius was defeated and killed at Plataea.
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