came from the northern grasslands of what is now Uzbekistan, sometime in the first millennium BC; when these nomads settled in the region they built an extensive irrigation system along the rivers. At this time, cities such as Bukhoro (Bukhara) and Samarqand (Samarkand) emerged as centres of government and high culture. By the fifth century BC, the Bactrian, Sogdian, and Tokharian states dominated the region. As East Asian countries began to develop its silk trade with the West, Persian cities took advantage of this commerce by becoming centres of trade. Using an extensive network of cities and rural settlements in the province of Transoxiana, and further east in what is today China's Xinjiang Uygur Autonomous Region, the Sogdian intermediaries became the wealthiest of these Iranian merchants. As a result of this trade on what became known as the Silk Route, Bukhara and Samarkand eventually became extremely wealthy cities, and at times Transoxiana (Mawarannahr) was one of the most influential and powerful Persian provinces of antiquity. In 327 BC Macedonian ruler Alexander the Great conquered the Persian Empire provinces of Sogdiana and Bactria, which contained the territories of modern Uzbekistan. A conquest was supposedly of little help to Alexander as popular resistance was fierce, causing Alexander's army to be bogged down in the region that became the northern part of the Macedonian Greco-Bactrian Kingdom. The kingdom was replaced with the Yuezhi dominated Kushan Empire in the first century BC. For many centuries the region of Uzbekistan was ruled by the Persian empires, including the Parthian and Sassanid Empires, as well as by other empires, for example, those formed by the Turko-Persian Hephthalite and Turkic Gokturk peoples. The Muslim conquests from the seventh century onward assisted the Arabs to bring Islam to Uzbekistan. In the same period, it began to take roots within the nomadic Turkic peoples who accepted the religion. In the eighth century, Transoxiana, the territory between the Amudarya and Syrdarya rivers, was conquered by the Arabs (Qutayba ibn Muslim) becoming a focal point soon after the Islamic Golden Age. Among the achievements of scholars during this period were the development of trigonometry into its modern form (simplifying its practical application to calculate the phases of the moon), advances in optics, in astronomy, as well as in poetry, philosophy, art, calligraphy, and many others, which set the foundation for the Muslim Renaissance. In the ninth and tenth centuries, Transoxiana was