The heyday of the Archaic period tyrants came in the early 6th century BC, when Cleisthenes ruled Sicyon in the Peloponnesus and Polycrates ruled Samos. During this time, revolts overthrew many governments in the Aegean world. Chilon, the ambitious and capable ephor of Sparta, built a strong alliance amongst neighbouring states by making common cause with these groups seeking to oppose unpopular tyrannical rule. By intervening against the tyrants of Sicyon, Corinth and Athens, Sparta thus came to assume Hellenic leadership prior to the Persian invasions. Simultaneously Persia first started making inroads into Greece, and many tyrants sought Persian help against popular forces seeking to remove them