 Complete the following phrase:  From March to September 1937, Lützow, now an Oberleutt first lieutet, claimed five victories, including the first ever recorded claim by a Messerschmitt Bf 109 pilot. Flying a Bf 109 B, he shot down a Polikarpov I-15, a Soviet built biplane fighter aircraft, on 6 April 1937. On 26 April 1937, air elements of the Condor Legion targeted and 