 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.