In 340, when Philip assembled a large Macedonian army and invaded Thrace, he left his 16 years old son with the power to rule Macedonia in his absence as regent, which shows that even at such young age Alexander was recognized as quite capable. But as the Macedonian army advanced deep into Thrace, the Thracian tribe of Maedi bordering north-eastern Macedonia rebelled and posed a danger to the country. Alexander assembled an army, led it against the rebels, and with swift action defeated the Maedi, captured their stronghold, and renamed it after himself to Alexandropolis. Two years later in 338 BC, Philip gave his son a commanding post among the senior generals as the Macedonian army invaded Greece. At the Battle of Chaeronea the Greeks were defeated and Alexander displayed his bravery by destroying the elite Greek force, the Theban Secret Band. Some ancient historians recorded that the Macedonians won the battle thanks to his bravery.