Thracia or Thrace ( Thrakē) is the ancient name given to the southeastern Balkan region, the land inhabited by the Thracians. Thrace was ruled by the Odrysian kingdom during the Classical and Hellenistic eras, and briefly by the Greek Diadochi ruler Lysimachus, but became a client state of the late Roman Republic and early Roman Empire as the Sapaean kingdom. Roman emperor Claudius annexed the kingdom as a Roman province in 46 AD. Confines From the perspective of classical Greece, Thracia included the territory north of Thessaly, with no definite boundaries,<ref>{{cite book |first=Thomas |last=Swinburne Carr |title=The history and geography of Greece |publisher=Simpkin, Marshall & Company |year=1838 |page=56 |url=https://archive.org/details/historyandgeogr00carrgoog }}</ref> sometimes to the inclusion of Macedonia and Scythia Minor. Later, Thracia proper was understood to include the territory bordered by the Danube on the north, by the Black Sea on the east, by Macedonia in the south and by Illyria to the west, roughly equivalent with the territory of the Thracian kingdom as it stood during the 5th to 1st centuries BC. With the annexation of the Thracian kingdom by the Roman Empire, by order of emperor Claudius, in AD 46, Thracia (formally provincia Thracia "Thracian province", "eparchy of the Thracians") was established as a Roman province. After the administrative reforms of the 3rd century, Thracia was reduced to the territory of the six small provinces of the Diocese of Thrace. Later still, the medieval Byzantine theme of Thracia contained only what today is Eastern Thrace. Under the Principate The Odrysian kingdom of Thrace became a Roman client kingdom c. 20 BC, while the Greek city-states on the Black Sea coast came under Roman control as civitates foederatae ("allied" cities with internal autonomy). After the death of the Thracian king Rhoemetalces III in 46 AD and an unsuccessful anti-Roman revolt, the kingdom was annexed as the Roman province of Thracia. The new province encompassed not only the lands of the former Odrysian realm, but also the north-eastern portion of the province of Macedonia as well as the islands of Thasos, Samothrace and Imbros in the Aegean Sea. To the north, Thracia bordered the province of Moesia Inferior; initially, the provincial boundary ran at a line north of the Haeumus Mountains, including the cities of Nicopolis ad Istrum and Marcianopolis in Thracia, but by the end of the 2nd century AD the border had moved south along the Haemus. The area of