Anticipating a firm Allied reaction should the main thrust of the invasion take place through the Netherlands, Manstein devised an innovative operation—later known as the "Sichelschnitt" ("sickle cut")—that called for an attack through the woods of the Ardennes and a rapid drive to the English Channel, thus cutting off the French and Allied armies in Belgium and Flanders. Attaining the rank of general at the end of the campaign, he was active in the invasion of the Soviet Union in June 1941. He led the Axis forces in the siege of Sevastopol (1941–1942) and the Battle of the Kerch Peninsula, and was promoted to field marshal on 1 July 1942, after which he participated in the siege of Leningrad.