 Complete the following phrase:  On 1 July 1943, Jagdgruppe Nord des 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 25 and was commanded by Oberstleutt Herbert Ihlefeld. Both JG 25 and its sister unit Jagdgeschwader 50 were ultimately unsuccessful in effectively countering the Mosquito and were more profitably used for interception of the US heavy bomber formations during the 