A country of west-central Asia east of the Caspian Sea. Once part of ancient Persia and later ruled by Arabs (8th century), Turks (11th century), Mongols (13th-14th century), and Uzbeks (late 15th century), it was annexed by Russia in 1881 and became a constituent state of the USSR, the Turkmen Soviet Socialist Republic, in 1925. Turkmenistan declared its independence in 1991 following the collapse of the Soviet Union. Ashgabat is the capital and the largest city.