Sogdians
The Sogdians were an ancient people of Central Asia, who inhabited the region known to the West as Sogdiana. Sogdiana covered much of the territory of modern-day Tajikistan, southern Uzbekistan, and northern Afghanistan. The Sogdian state was centered around its capital city of Afrasiab, which was situated where the modern city of Samarkand now stands, in southeastern Uzbekistan. They occupied a key position along the ancient Silk Road, and played a major role in facilitating trade between China and Central Asia.
The Sogdians were noted for their tolerance of different religious beliefs, and Buddhism, Manichaeism, Nestorian Christianity, and Zoroastrianism all had significant followings. Much of our knowledge of the Sogdians and their language comes from the numerous religious texts that they have left behind.
The Sogdians spoke an East Iranian language called Sogdian, which was closely related to Bactrian, another major language of the region in ancient times. Sogdian was written in a variety of scripts, all of which were derived from Aramaic.
Following the conquest of Central Asia by Alexander the Great in the 4th century BC (despite ferocious local resistance), Sogdiana was ruled by a series of foreign rulers, including Greeks, Hepthalites, Turks, and Mongols. The great majority of the Sogdian people gradually mixed with other local Iranian groups such as the Bactrians and came to speak the Tajik dialect of Persian. Numerous Sogdian words can be found in Tajik Persian as a result of this admixture. The Sogdian language continued to be spoken in a small part of the area, and is today known as Yaghnobi.
[Sources: www.iranianlanguages.com, Dupree, Louis. Afghanistan. Princeton: Princeton University Press, 1980]
