He became such, because the Athenians had made an alliance with his brother Philip and Derdas, when acting together against him.

And being alarmed, he both sent to Lacedaemon, and tried to contrive that they might be involved in war with the Peloponnesians, and endeavoured to win over the Corinthians, with a view to Potidaea's revolting;

and made proposals also to the Thrace-ward Chalcidians and the Bottiaeans to join in the revolt, thinking that if he had in alliance with him these places on his borders, he should more easily carry on the war in conjunction with them.