 Complete the following phrase:  On 21 July 1943, Jagdgruppe Süd der ObdL was formed as a high-altitude fighter unit to combat the RAFs Mosquito twin-engine bomber and reconnaissance aircraft. On 15 August 1943 the unit was redesignated Jagdgeschwader 50 and was commanded by Major Hermann Graf, the first pilot in history to achieve 200 aerial victories. It was planned to equip JG 50 with the Messerschmitt Me 163 rocket fighter and began training on glider aircraft. Both JG 50 and its sister unit Jagdgeschwader 25 were ultimately unsuccessful in effectively countering the Mosquito and were more successfully used for interception of the US heavy bomber formations during the 