Before the reign of Alexander I, father of Perdiccas II, the ancient Macedonians lived mostly on lands adjacent to the Haliakmon, in the far south of the modern Greek province of Macedonia. Alexander is credited with having added to Macedonia many of the lands that would become part of the core Macedonian territory: Pieria, Bottiaia, Mygdonia, and Eordaia (Thuc. 2.99). Anthemus, Crestonia, and Bisaltia also seem to have been added during his reign (Thuc. 2.99). Most of these lands were previously inhabited by Thracian tribes, and Thucydides records how the Thracians were pushed to the mountains when the Macedonians acquired their lands.