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 as the spring rasputitsa had subsided. On 13 March, Hitler signed Operational Order No. 5, which authorised several offensives, including one against the Kursk salient. As the last Soviet resistance in Kharkov petered out, Manstein attempted to persuade Günther von Kluge, commander of Army Group Centre, to immediately attack the Central Front, which was defending the northern face of the salient. Kluge refused, believing that his forces were too weak to launch such an attack. Further Axis advances were blocked by Soviet forces that had been shifted down from the Central Front to the area north of Belgorod. By mid-April,