On 3 and 4 February 1942, Clausen and "Oberleutnant" Friedrich Geißhardt shot down three Polikarpov R-5s or Polikarpov R-Zs of 622 LBAP ("Legkii Bombardirovochnyy Aviatsionyy Polk"—Light Bomber Aviation Regiment) and 672 LBAP. Clausen became an "ace-in-a-day" for the first time on 9 March 1942, claiming aerial victories 36 to 40. Following the Battle of the Kerch Peninsula, his total had reached 52 aerial victories on 6 April 1942. For this he was awarded the German Cross in Gold () on 18 May 1942, a direct presentation by "Reichsmarschall" Hermann Göring. Four days later, he was also honored with the Knight's Cross of the Iron Cross ().