This book examines the history of one of the historical and cultural regions of Central Asia, lying north of the Amu Darya, within the upper and middle basins of the great Central Asian river. These lands constituted the zone of the country already mentioned in the oldest parts of Avesta as Bahdi, in Greco-Roman sources - as Bactria or Bactriana, and in Chinese chronicles of the first centuries BC. e. - as Dahya or the country of Tu-ho-lo - the distorted name of the Tohar tribe, which name - in the local pronunciation of Toharistan - was preserved here in the Middle Ages.