Seeking to secure his empire from further revolts and from the interference of the mainland Greeks, Darius embarked on a scheme to conquer Greece and to punish Athens and Eretria for the burning of Sardis. The first Persian invasion of Greece began in 492 BC, with the Persian general Mardonius successfully re-subjugating Thrace and Macedon before several mishaps forced an early end to the rest of the campaign. In 490 BC a second force was sent to Greece, this time across the Aegean Sea, under the command of Datis and Artaphernes. This expedition subjugated the Cyclades, before besieging, capturing and razing Eretria. However, while en route to attack Athens, the Persian force was decisively defeated by the Athenians at the Battle of Marathon, ending Persian efforts for the time being.