Achaemenid Macedonia refers to the period the ancient Greek Kingdom of Macedonia was under the Achaemenid Persian sway. In 512/511 BC, Megabyzus forced the Macedonian king Amyntas I to make his kingdom a vassal of the Achaemenids. In 492, following the Ionian Revolt, Mardonius firmly re-tightened the Persian grip in the Balkans, and made Macedon a fully subordinate kingdom within the Achaemenid domains, part of its administrative system, until the definite withdrawal of the Persians from their European territories following the eventual failure at the Second Persian invasion of Greece.