For the Persians, the only unfinished business that remained by the end of 493 BC was to exact punishment on Athens and Eretria for supporting the revolt. The Ionian Revolt had severely threatened the stability of Darius's empire, and the states of mainland Greece would continue to threaten that stability unless dealt with. Darius thus began to contemplate the complete conquest of Greece, beginning with the destruction of Athens and Eretria. The first Persian invasion of Greece thus began in the following year, 492 BC, when Mardonius was dispatched (via Ionia) to complete the pacification of the land approaches to Greece, and push on to Athens and Eretria if possible. Thrace was re-subjugated, having broken loose from Persian rule during the revolts, and Macedon compelled to become a vassal of Persia. However, progress was halted by a naval disaster. A second expedition was launched in 490 BC under Datis and Artaphernes, son of the satrap Artaphernes. This amphibious force sailed across the Aegean, subjugating the Cyclades, before arriving off Euboea. Eretria was besieged, captured and destroyed, and the force then moved onto Attica. Landing at the Bay of Marathon, they were met by an Athenian army, and defeated in the famous Battle of Marathon, ending the first Persian attempt to subdue Greece.