Later, in the Classical period, the leagues were fewer and larger, and dominated by one city (particularly Athens, Sparta and Thebes). Often cities would be compelled to join under threat of war (or as part of a peace treaty). After Philip II of Macedon 'conquered' the heartlands of ancient Greece, he did not attempt to annex the territory, or unify it into a new province. However, he did force most of the cities to join his own Corinthian League.