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 well as the re-subjugation of Thrace and the conquering of Macedonia in 492 BC under Mardonius. Macedon had been a vassal kingdom of the Persians since the late 6th century BC, but retained autonomy. Mardonius' 492 campaign made it a fully subordinate part of the Persian kingdom. These military actions, coming as a direct response to the revolt in Ionia, were the beginning of the First Persian invasion of (mainland) Greece. At the same time, anti-Persian parties gained more power in Athens, and pro-Persian aristocrats were exiled from Athens and Sparta.