The night before the start of the operations, the Soviet night bombers attacked the German divisional headquarters and artillery positions to disrupt the German command and control. The bombers also attacked German airfields and communication centres to disrupt the flow of reinforcements. Operation Iskra began at 9:30 on 12 January, when the two Soviet fronts began their artillery preparation, which lasted for nearly two and a half hours on the western side and nearly two hours on the eastern side of the bottleneck. The Soviet attack started five minutes before the artillery preparation finished with a "Katyusha" barrage, to fully exploit its effects.