Perekop, Isthmus of (pĕrĭkôpˈ) [key], c.19 mi (30 km) long and from 5 to 14 mi (8–23 km) wide, S Ukraine, connecting the Crimea with the Ukrainian mainland. It separates the Gulf of Perekop (an arm of the Black Sea) in the west from the Sivash Sea (an inlet of the Sea of Azov) in the east. Because of its strategic position and economic importance (salt extraction from the lakes in the southern part), the Greeks and Tatars fortified the isthmus with moats and ramparts and the Tatars built a fortress on the site of the village of Perekop and called it Or-Kapi; there are ruins of the Greek and Tatar fortifications. The Greeks and Byzantines called the isthmus Taphros. Before the 15th cent. there was a Genoese colony there. The isthmus passed to Russia in 1783. There the Red Army decisively defeated (1920) Wrangel in the Russian civil war. In 1944 the Germans were routed out of the Crimea north of the isthmus. The isthmus was transferred with the Crimea to the Ukrainian SSR (now Ukraine) in 1954.