Greater Iran (Persian: ایران بزرگ, Irān-e Bozorg, ایران زَمین, Irānzamīn) refers to the regions of the Caucasus, West Asia, Central Asia, and South Asia that have significant Iranian cultural influence due to having been either long historically ruled by the various Iranian and Persian empires (such as those of the Medes, Achaemenids, Parthians, Sassanians, Samanids, Safavids, and Afsharids and the Qajar Empire), having considerable aspects of Persian culture in their own culture due to extensive contact with the various Empires based in Persia (e.g., those regions and peoples in the North Caucasus that were not under direct Iranian rule), or are simply nowadays still inhabited by a significant amount of Iranian people who patronize their respective cultures (as it goes for the western parts of South Asia, Bahrain and China). It roughly corresponds to the territory on the Iranian plateau and its bordering plains. It is also referred to as Greater Persia, while the Encyclopædia Iranica uses the term Iranian Cultural Continent.The term Iran is not limited to the modern state of Iran (Persia), but includes all the territory ruled by the Iranians, including Mesopotamia, Eastern Anatolia, all of the Caucasus and Central Asia. The concept of Greater Iran has its source in the history of the First Persian (Achaemenid) Empire in Persis (Fars), and is in fact synonymous with the history of Iran in many respects.After the Arab conquests, Iran lost many of the territories gained under the Safavid dynasty, including Iraq to the Ottomans (via Treaty of Amasya in 1555 and Treaty of Zuhab in 1639), Afghanistan to the British (via Treaty of Paris in 1857 and MacMahon Arbitration in 1905), and all its Caucasus territories to Russia during the Russo-Persian Wars in the course of the 19th century. The Treaty of Gulistan in 1813 resulted in Iran ceding Dagestan, Georgia, and most of Azerbaijan to Russia. The Turkmanchey Treaty of 1828, after the Russo-Persian War (1826-1828) permanently severed the Caucasian provinces from Iran, which had made part of its concept for three centuries, and forced Iran to cede modern-day Armenia, Azerbaijan and minor parts of Eastern Turkey, and settled the modern boundary along the Aras River.Due to this geographic diversity, newly independent nations under Russian or British involvement, while maintaining a cultural or linguistic connection with Persia, developed their own unique socio-political and cultural paths. Some of these nations and territories included Armenia, Azerbaijan, Bahrain, Georgia, Iraq, Dagestan, Turkmenistan, Uzbekistan, and Afghanistan. In 1935 under the rule of Reza Shah, the endonym Iran was made the official international name.