Commencing at 06:45 on 6 April, the "Luftwaffe" launched Operation Retribution, a series of concerted bombing attacks on Belgrade that coincided with air and ground attacks throughout the country. Several waves of German aircraft approached Belgrade during the day, initially Junkers Ju 87 "Stuka" dive-bombers escorted by fighters. All of the Bf 109E-3s of the 51st Fighter Group scrambled to meet the first onslaught, and they were soon joined by the Messerschmitts of 32nd Fighter Group. Seven claims were made by the pilots of the 102nd Squadron of the 51st Fighter Group, losing five aircraft in return. The 32nd Fighter Group Messerschmitts claimed another four bombers for the loss of two of their own, although several more Yugoslav fighters were hit and damaged. During the initial melee, Yugoslav anti-aircraft guns had fired at the Yugoslav Messerschmitts as well as the German ones, unable to distinguish between them.