Old Thasian settlement in Kavála, Greece, which Philip II of Macedon fortified in 356 BC to control neighboring gold mines. In 42 BC Philippi was the site of the decisive Roman battle in which Mark Antony and Octavian (later the emperor Augustus) defeated Brutus and Cassius, the leading assassins of Julius Caesar. Located in Thrace, it was the object of an unsuccessful attempt at colonization by Thasos in the 6th century BC and for a time was known as Crenides and Daton. After his victory, Mark Antony established Philippi as a colonia for his veterans, and the town gained strategic importance from its position and its proximity to the port of Neapolis. Philippi was important in the early history of Christianity, as is shown by the prominence given to the story of St. Paul preaching there in 49 AD and being consequently imprisoned and extensive early Christian building. Among the ruins are walls, acropolis, forum, gymnasium, macellum, baths, and theaters.