After Chaeronea, Philip inflicted a harsh punishment upon Thebes, but made peace with Athens on very lenient terms. Demosthenes encouraged the fortification of Athens and was chosen by the ekklesia to deliver the Funeral Oration. In 337 BC, Philip created the League of Corinth, a confederation of Greek states under his leadership, and returned to Pella. In 336 BC, Philip was assassinated at the wedding of his daughter, Cleopatra of Macedon, to King Alexander of Epirus. The Macedonian army swiftly proclaimed Alexander III of Macedon, then twenty years old, as the new King of Macedon. Greek cities like Athens and Thebes saw in this change of leadership an opportunity to regain their full independence. Demosthenes celebrated Philip's assassination and played a leading part in his city's uprising. According to Aeschines, "it was but the seventh day after the death of his daughter, and though the ceremonies of mourning were not yet completed, he put a garland on his head and white raiment on his body, and there he stood making thank-offerings, violating all decency." Demosthenes also sent envoys to Attalus, whom he considered to be an internal opponent of Alexander. Nonetheless, Alexander moved swiftly to Thebes, which submitted shortly after his appearance at its gates. When the Athenians learned that Alexander had moved quickly to Boeotia, they panicked and begged the new King of Macedon for mercy. Alexander admonished them but imposed no punishment.