Khwarazm (khwärăz´əm) or Khorezm (khərĕz´əm), ancient and medieval state of central Asia, situated in and around the basin of the lower Amu Darya River; now a region, NW Uzbekistan. Khwarazm is one of the oldest centers of civilization in central Asia. It was a part of the Achaemenid empire of Cyrus the Great in the 6th cent. BC and became independent in the 4th cent. BC It was later inhabited by Indians who adhered to Zoroastrianism and used Aramaic script. Khwarazm was conquered by the Arabs in the 7th cent. and was converted to Islam. In 995 the country was united under the emirs of N Khwarazm, whose capital Urgench became a major seat of Arabic learning. The capital was a center of agriculture and trade and the residence of the ruling shahs. In the late 12th cent., Khwarazm gained independence from the Seljuk Turks. With independence it expanded its rule, and at the height of its power in the early 13th cent. ruled from the Caspian Sea to Bukhara and Samarkand. It was conquered in 1221 by Jenghiz Khan and was included in the Golden Horde. The development of caravan trade by the Mongols was profitable to Khwarazm. In the late 14th cent., Khwarazm, along with its vast irrigation system, was destroyed by Timur (Tamerlane). A century of struggle over Khwarazm between the Timurids, the descendants of Timur, and the Golden Horde was followed by the Uzbek conquest in the early 16th cent. Khwarazm became an independent Uzbek state and was known as the khanate of Khiva after Khiva became the capital. There are ruins of ancient forts, one of which dates back to the 6th cent. BC