The Sogdians came to Sogdiana (parts of modern Tajikistan and Uzbekistan) probably about 1500 BC. They were part of the wave of Indo-European migration to the south-east. Many people left Georgia and Armenia about that time and moved to Iran and northern India. So the Sogdians, like their Persian and Indian neighbors, were Indo-Europeans. Their language was closely related to Persian. Like other Indo-Europeans, they brought with them their horses and chariots. The Sogdians’ main city was Marakanda (now Samarkand).
When Cyrus the Great conquered the lands around Persia to form the Persian Empire in 526 BC, one of the kingdoms he conquered was Sogdiana. The Sogdians were part of the Persian Empire until 325 BC. The Sogdians had a big fort called the Sogdian Rock or the Rock of Arimazes. Near this fort, at Takhti Sangin, there was a magnificent collection of gold and silver now known as the Oxus Treasure.
Probably the reason the Sogdians had so much gold and silver was that they were traders, selling horses and cattle to China and Persia, and also selling Chinese silk to Persia and Persian silver and glass beads to China. Many of the Sogdian men were great soldiers who helped to protect the Persians against the nomadic Scythians to their north.