Province of ancient Persia.
It was centred in the fertile valley of the Zeravshan River, in modern Uzbekistan. It became a satrapy of the Achaemenian dynasty under Darius I in the 6th century BC and was conquered by Alexander the Great in the 4th century. It asserted its independence from the Seleucid dynasty с 250 BC as part of the Bactrian kingdom (see Bactria ) and fell to invading northern tribes in the 2nd century BC. It prospered as a centre of Islamic civilization, especially under the Sāmānid dynasty (9th–10th centuries AD), until the Mongol invasion of the 13th century. See also Bukhara .