A cursory mention of a mysterious expedition against Sicyon, mounted by Thrasybulus, the tyrant of Miletus, can be found in Frontinus’ “Strategemata”. The author of the present article is of the opinion that in this way Thrasybulus was helping his ally Periander, the tyrant of Corinth. The probable aim of Periander’s military campaign was to reinstate the exiled Isodemus as tyrant of Sicyon and to include the Sicyonians’ territory in Corinth’ sphere of influence.