ancient country of Central Asia centring on the fertile valley of the Zeravshan River, in modern Uzbekistan. Excavations have shown that Sogdiana was probably settled between 1000 and 500 BC and that it then passed under Achaemenian rule. It was later attacked by Alexander the Great and may have been included in the Bactrian Greek kingdom until the invasions of Saka and Yuezhi peoples in the 2nd century BC. Sogdiana remained a prosperous centre until the Mongol invasions. Under the Sāmānid dynasty (9th–10th century AD) it was an eastern focal point of Islamic civilization.