 From March to September 1937, Lützow, now an "Oberleutnant" (first lieutenant), 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 bombed Guernica, an attack which has been characterised as a war crime by Wette and Ueberschär, but Lützow did not participate in the attack as he was on home leave from 8–29 April 1937.