relatively successful. As presented by Herodotus, the tactics used by the Scythians resulted in the loss of their best lands and of damage to their loyal allies. This gave Darius the initiative. As he moved eastwards in the cultivated lands of the Scythians in Eastern Europe proper, he remained resupplied by his fleet and lived to an extent off the land. While moving eastwards in the European Scythian lands, he captured the large fortified city of the Budini, one of the allies of the Scythians, and burnt it. Darius eventually ordered a halt at the banks of Oarus, where he built "eight great forts, some distant from each other", no doubt as a frontier defence. In his Histories, Herodotus states that the ruins of the forts were still standing in his day. After chasing the Scythians for a month, Darius's army was suffering losses due to fatigue, privation and sickness. Concerned about losing more of his troops, Darius halted the march at the banks of the Volga River and headed towards Thrace. He had conquered enough Scythian territory to force the Scythians to respect the Persian forces. Persian invasion of Greece Darius's European expedition was a major event in his reign, which began with the invasion of Thrace. Darius also conquered many cities of the northern Aegean, Paeonia, while Macedonia submitted voluntarily, after the demand of earth and water, becoming a vassal kingdom. He then left Megabyzus to conquer Thrace, returning to Sardis to spend the winter. The Greeks living in Asia Minor and some of the Greek islands had submitted to Persian rule already by 510 BCE. Nonetheless, there were certain Greeks who were pro-Persian, although these were largely based in Athens. To improve Greek-Persian relations, Darius opened his court and treasuries to those Greeks who wanted to serve him. These Greeks served as soldiers, artisans, statesmen and mariners for Darius. However, the increasing concerns amongst the Greeks over the strength of Darius's kingdom along with the constant interference by the Greeks in Ionia and Lydia were stepping stones towards the conflict that was yet to come between Persia and certain of the leading Greek city states. When Aristagoras organized the Ionian Revolt, Eretria and Athens supported him by sending ships and troops to Ionia and by burning Sardis. Persian military and naval operations to quell the revolt ended in the Persian reoccupation of Ionian and Greek islands, as