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
Orel–Kursk operation White shock group, opening the way for the Red advance on Kharkov and the Donbass. Along with the simultaneous Voronezh–Kastornoye operation, it marked a turning point in the fight against the Armed Forces of South Russia, creating favorable conditions for the advance of the Southern and Southeastern Fronts in 1919 and 1920. The loss of Kursk and Kastornoye broke White morale, preventing them from resisting the Red advance in pitched battle, and precipitated a White retreat that lasted until they reached the North Caucasus. The strategic initiative on the front was gained by the Red Army, but it did not