A country of southwest Asia. Inhabited since c. 2000 bc by Iranian peoples, the region later became the core of the Persian Empire. After being conquered by Alexander the Great and ruled by the Parthian Arsacid dynasty, Persia was reestablished under the Sassanian dynasty ( ad 224–651) and, after invasions by Arabs (7th century), Turks (10th century), and Mongols (13th century), was reestablished again under the Safavid dynasty (1502–1736). The country, renamed Iran in 1935, was ruled by the Pahlavi dynasty from 1925 until the ouster of Mohammad Reza Pahlavi (1979) in a revolution led by the Ayatollah Khomeini, who established an Islamic republic. Tehran is the capital and the largest city.