The history of Turkmenistan traditionally began with the arrival of Indo-European Iranian tribes around 2000 BC. Early tribes were nomadic or semi-nomadic due to the arid conditions of the region that prevented widespread adoption of agriculture, and the steppe culture in Central Asia was an extension of a larger Eurasian series of horse cultures which spanned the entire spectrum of language families, including the Indo-Europeans and Turko-Mongol groups. Some of the known early Iranian tribes included the Massagatae, the Scythians/Sakas, and early Soghdians, who were most likely precursors of the Khwarezmians. Turkmenistan was a passing point for numerous migrations and invasions by tribes, which gravitated towards the settled regions of the south, including ancient Mesopotamia, Elam, and the Indus Valley civilization. The region's written history begins with the region's conquest by the Achaemenid Empire of Ancient Iran, as the region was divided between the satraps of Margiana, Chorasmia and Parthia. Later conquerors included Alexander the Great, the Parni, Ephthalites, Iranian Huns, Göktürks, Sarmatians, and Sassanid Iranians. During this early phase of history, the majority of Turkmenistan's inhabitants were adherents of Zoroastrianism and Buddhism, and the region was largely dominated by Iranian peoples. These incursions and epochs, though pivotal, did not shape the region's history as the invasions of two later invading groups: Arabs and the Oghuz Turks. The vast majority of inhabitants were converted to Hanifism, while the Oghuz brought the beginnings of the Turkic Turkmen language that came to dominate the area. The Turkic period was a time of cultural fusion and growth, as Islamic traditions brought by the Arabs merged with local Iranian cultures, and the city of Merv became a centre of commerce, science, and innovation, being an influential capital of several Islamic caliphates. The cultural landscape of Turkmenistan was further altered by Turkic invaders and rulers such as the Seljuks. Genghis Khan and Mongol invasions devastated the region during the late Middle Ages, but their hold upon the area was transitional as Timur Leng and Uzbeks later contested the land. Modern Turkmenistan was radically transformed by the invasion of the Russian Empire, which conquered and annexed the region in the late 19th century. Later, the Russian Revolution of 1917 would ultimately transform Turkmenistan from an Islamic and nomadic tribal society to an industrialized and urbanist Leninist socialist republic during the Soviet era. Independence came in 1991, as Saparmurat Niyazov, a former member of the local branch