Transoxiana: the land beyond the Oxus that every empire wanted
Between two great Central Asian rivers lies a stretch of dry but fertile plain that Persians, Greeks, Arabs, Chinese and Mongols all fought to hold. Its Latin name means simply the land beyond the Oxus. Each conqueror renamed it, yet Samarkand and Bukhara kept Persian culture alive through them all.
Geographically, the region sits between the Amu Darya, the ancient Oxus, to the south and the Syr Darya to the north, covering roughly eastern Uzbekistan, western Tajikistan, southern Kyrgyzstan and parts of Kazakhstan and Turkmenistan. Nearly every culture that touched it named it by its river. Persians said Farā-rūd, beyond the river; Arabs said Mā Warāʾ an-Nahr, what is beyond the river; the Chinese called it Hezhong, land between rivers. Ancient Iranians knew it as Turan, the name used in the epic Shahnameh.
Under the Achaemenids it was the province of Sogdia. The Western label stuck because of Alexander the Great, whose invasion in the 4th century BCE brought Greek culture, and whose successors founded the Greco-Bactrian Kingdom, which lasted over two hundred years. Its only extensively excavated city is Ai-Khanoum on the Oxus in northern Afghanistan. The Chinese envoy Zhang Qian passed through in 126 BCE, writing the first known Chinese report on the area. Later, wealth from the Northern Silk Road made it a cultural centre under the Sasanians, though Hephthalite invaders interrupted their rule until 565 CE.
Arab armies under Qutayba ibn Muslim conquered much of it between 706 and 715, and control passed from the Umayyads to the Abbasids in 750. Before then, the inhabitants spoke Sogdian, an Iranian language, and followed local forms of Zoroastrianism alongside Buddhism, Nestorian Christianity and Manichaeism. That religious mix faded after the conquest. Paradoxically, Arab rule also spread New Persian as a spoken and then written language, and Samarkand and Bukhara helped revive Persian culture through the Samanid Empire.
Genghis Khan invaded in 1219 while conquering Khwarezm, and before his death in 1227 he gave the region to his son Chagatai, whose name the khanate took. In 1369 Timur of the Barlas tribe took effective control and made Samarkand the capital of the empire he went on to build.
Source: Transoxiana