Battle of Kursk guns and mortars. In 1943 an offensive by the Soviet Central, Bryansk and Western Fronts against Army Group Centre was abandoned shortly after it began in early March, when the southern flank of the Central Front was threatened by Army Group South. Soviet intelligence received information about German troop concentrations spotted at Orel and Kharkov, as well as details of an intended German offensive in the Kursk sector through the Lucy spy ring in Switzerland. The Soviets verified the intelligence via their spy in Britain, John Cairncross, at the Government Code and Cypher School at Bletchley Park, who clandestinely forwarded
Battle of Kursk term blitzkrieg (lightning war); other military historians do not use the term in their works on the battle. Operation Citadel called for a double envelopment, directed at Kursk, to surround the Soviet defenders of five armies and seal off the salient. Army Group Centre would provide General Walter Model's 9th Army to form the northern pincer. It would cut through the northern face of the salient, driving south to the hills east of Kursk, securing the rail line from Soviet attack. Army Group South would commit the 4th Panzer Army, under Hermann Hoth, and Army Detachment "Kempf", under Werner Kempf,