The boundaries of Thrace have always been vague: the only fixed point is that Istanbul and the Bosphorus stand at its eastern edge. For the last 200 years or so the name has meant the segment of Europe within about 400 km of Istanbul. The ancient Thracian people occupied a larger region, and the term "Europe" was first applied to their lands. In Greek mythology they were the tribe of Thrax, son of Ares the god of war - they were described as warlike, but those accounts reflect times when they were in conflict with Persia, Greece or Rome. They were probably an Indo-European people who became distinct from the Dacians of Romania around 1000 BC. They were united as the Odrysian kingdom from the 5th to 3rd century BC but were otherwise disparate. They became assimilated into Ancient Greece and the Roman Empire and vanished, leaving a legacy of artworks, burial mounds, and some place name elements. From medieval times their region lay within the Ottoman Empire.
The present layout of Thrace reflects the 1923 Treaty of Lausanne, which adjusted national borders after the Great War, and mandated population exchanges to reduce ethnic tensions:
- Northern Thrace (Северна Тракия) or Upper Thracian Plain is in Bulgaria.
- Western Thrace (Θράκη) comprises three prefectures of Greece: Evros (which includes the island of Samothrace), Rhodope and Xanthi.
- Eastern Thrace (Doğu Trakya or Rumeli) is the European part of Turkey. Although geographically this includes Istanbul, that's a metropolitan region spanning both sides of the Bosphorus and described on separate pages.
All three countries usually refer to their portion as simply Thrace, since from their point of view the geography is inverted: thus in Turkey "Eastern Thrace" is the furthest west of the entire country, and so on. In each, "Thracian" is a distinct regional identity, but of course refers to modern inhabitants. The original Thracians disappeared from history around the 4th century AD, and after 1600 years of subsequent conquests and civilisations in the region, it's difficult to learn much about them.