Until the age of 16, Alexander was tutored by Aristotle. In 335 BC, shortly after his assumption of kingship over Macedon, he campaigned in the Balkans and reasserted control over Thrace and parts of Illyria before marching on the city of Thebes, which was subsequently destroyed in battle. Alexander then led the League of Corinth, and used his authority to launch the pan-Hellenic project envisaged by his father, assuming leadership over all Greeks in their conquest of Persia.