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 of powerful Soviet concentrations behind the Kursk area, Hitler further delayed the offensive to allow for more equipment to reach the front. With pessimism for Citadel increasing with each delay, in June, Alfred Jodl, the Chief of Staff at the OKW, instructed the armed forces propaganda office to portray the upcoming operation as a limited counteroffensive. Due to concerns of an Allied landing in the south of France or in Italy and delays in deliveries of the new tanks, Hitler postponed again, this time to 20 June. Zeitzler was profoundly concerned with the delays, but he still supported the offensive.