School at Bletchley Park, who clandestinely forwarded raw decrypts directly to Moscow. Cairncross also provided Soviet intelligence with identifications of the Luftwaffe airfields in the region. Soviet politician Anastas Mikoyan wrote that on 27 March 1943, Soviet leader Joseph Stalin notified him of a possible German attack in the Kursk sector. Stalin and some senior officers were eager to strike first once the rasputitsa ended, but a number of key officers, including Deputy Supreme Commander Georgiy Zhukov, recommended a strategic defensive before going on the offensive. In a letter to the Stavka and Stalin, on 8 April, Zhukov wrote: Stalin consulted with his frontline commanders and senior officers of the General Staff from 12 to 15 April 1943. In the end he and the Stavka agreed that the Germans would probably target Kursk. Stalin believed the decision to defend would give the Germans the initiative, but Zhukov countered that the Germans would be drawn into a trap where their armoured power would be destroyed, thus creating the conditions for a major Soviet counteroffensive. They decided to meet the enemy attack by preparing defensive positions to wear out the German groupings before launching their own offensive. Preparation of defences and fortifications began by the end of April, and continued until the German attack in early July. The two-month delay between the German decision to attack the Kursk salient and its implementation allowed the Red Army ample time to thoroughly prepare. The Voronezh Front, commanded by Nikolai Vatutin, was tasked with defending the southern face of the salient. The Central Front, commanded by Konstantin Rokossovsky, defended the northern face. Waiting in reserve was the Steppe Front, commanded by Ivan Konev. In February 1943, the Central Front had been reconstructed from the Don Front, which had been part of the northern pincer of Operation Uranus and had been responsible for the destruction of the 6th Army at Stalingrad. The Central and Voronezh Fronts each constructed three main defensive belts in their sectors, with each subdivided into several zones of fortification. The Soviets employed the labour of over 300,000 civilians. Fortifying each belt was an interconnected web of minefields, barbed-wire fences, anti-tank ditches, deep entrenchments for infantry, anti-tank obstacles, dug-in armoured vehicles, and machine-gun bunkers. Behind the three main defensive belts were three more belts prepared as fallback positions; the first was not fully occupied or heavily fortified, and the last two, though sufficiently