full strength in late April and early May. The strategic objective was illustrated after the victories of Erich von Manstein and the 11th Army in the Crimea. The main objective remained the Caucasus, its oil fields and as a secondary objective, the city of Stalingrad. The plan to begin Operation Fredericus in April led to more forces being allocated to the area of the German 6th Army. Unknown to the Soviet forces, the German army was regrouping in the center of operations for the offensive around Kharkov. On 10 May, Paulus submitted his final draft of Operation Fredericus and feared a Soviet attack. By then, the German army opposite Timoshenko was ready for the operation towards the Caucasus. Soviet offensive Initial success The Red Army offensive began at 6:30 a.m. on 12 May 1942, led by a concentrated hour-long artillery bombardment and a final twenty-minute air attack upon German positions. The ground offensive began with a dual pincer movement from the Vovchansk and Barvenkovo salients at 7:30 am. The German defences were knocked out by air raids, artillery-fire and coordinated ground attacks. The fighting was so fierce that the Soviets inched forward their second echelon formations, preparing to throw them into combat as well. Fighting was particularly ferocious near the Soviet village of Nepokrytaia (Shestakove), where the Germans launched three local counter-attacks. The Luftwaffe's fighter aircraft, despite their numerical inferiority, quickly defeated the Soviet air units in the airspace above the battle area, but without bombers, dive-bombers and ground-attack aircraft they could only strafe with their machine guns, drop small bombs on Soviet supply columns, and pin down infantry. By dark, the deepest Soviet advance was . Moskalenko, commander of the 38th Army, discovered the movement of several German reserve units and realised that the attack had been opposed by two German divisions, not the one expected, indicating poor Soviet reconnaissance and intelligence-gathering before the battle. A captured diary of a dead German general alluded to the Germans knowing about Soviet plans in the region. Next day Paulus obtained three infantry divisions and a panzer division for the defence of Kharkov and the Soviet advance was slow, achieving little success except on the left flank. Bock had warned Paulus not to counter-attack without air support, although this was later reconsidered, when several Soviet tank brigades broke through VIII Corps (General Walter Heitz) in the Volchansk sector, only from Kharkov. In