Having secured the northern (Thrace and up to the Istrus/Danube) and western (southern Illyria) frontiers of Macedonia and put down a revolt in Thebes in 335 BC, Alexander the Great crossed to Asia Minor in 334 as hegemon of the Panhellenic League (Corinthian League) to pursue the war of revenge against Persia which Philip II had declared in the spring of 337 (Diod. Sic. 17,17). No-one, ancient or modern, has been able to determine whether it was his intention from the outset to conquer the Persian Empire.