of Miletus, Aristagoras. The Persian Empire was still relatively young, and prone to revolts amongst its subject peoples. Moreover, Darius was a usurper, and had spent considerable time extinguishing revolts against his rule. The Ionian revolt threatened the integrity of his empire, and Darius thus vowed to punish those involved (especially those not already part of the empire). Darius also saw the opportunity to expand his empire into the fractious world of Ancient Greece. A preliminary expedition under Mardonius, in 492 BC, to secure the land approaches to Greece ended with the conquest of Thrace and forced Macedon to become a client kingdom of Persia. In 491 BC, Darius sent emissaries to all the Greek city-states, asking for a gift of 'earth and water' in token of their submission to him. Having had a demonstration of his power the previous year, the majority of the Greek cities duly obliged. In Athens, however, the ambassadors were put on trial and then executed; in Sparta, they were simply thrown down a well. This meant that Sparta was also now effectively at war with Persia. Darius thus put together an amphibious task force under Datis and Artaphernes in 490 BC, which attacked Naxos, before receiving the submission of the other Cycladic Islands. The task force then moved on Eretria, which it besieged and destroyed. Finally, it moved to attack Athens, landing at the bay of Marathon, where it was met by a heavily outnumbered Athenian army. At the ensuing Battle of Marathon, the Athenians won a remarkable victory, which resulted in the withdrawal of the Persian army to Asia. Darius therefore began raising a huge new army with which he meant to completely subjugate Greece; however, in 486 BC, his Egyptian subjects revolted, indefinitely postponing any Greek expedition. Darius then died whilst preparing to march on Egypt, and the throne of Persia passed to his son Xerxes I. Xerxes crushed the Egyptian revolt, and very quickly restarted the preparations for the invasion of Greece. Since this was to be a full-scale invasion, it required long-term planning, stock-piling and conscription. Xerxes decided that the Hellespont would be bridged to allow his army to cross to Europe, and that a canal should be dug across the isthmus of Mount Athos (rounding which headland, a Persian fleet had been destroyed in 492 BC). These were both feats of exceptional ambition, which would have been beyond any