Kammala jumla mai zuwa: A ranar 30 ga Satumba, "Gruppe" ya koma filin jirgin sama a Uetersen, yana tashi da ayyukan tsaro a kan Bight na Jamus. Unitungiyar ta ƙaura sau da yawa kuma tana tashi don kare Reich daga Esbjerg a ranar 10 ga Mayu, 1940, farkon Yaƙin Faransa. A ranar 14 ga Mayu, I. ((Jagd) "Gruppe" ya koma Essen-Mülheim don ayyukan da aka yi wa Faransa. A ranar 23 ga Mayu, sun sake komawa, wannan lokacin zuwa Ferme Montecouvez, filin jirgin sama kusan kudu da Cambrai. Kwana biyu bayan haka, I. ((Jagd) "Gruppe" an ba shi aikin ba da ragowar mayaƙa ga jigilar jigilar Jamusawa da ke sake ba da rundunar ta 4 a kusa da Cambrai. A wannan aikin, Clausen ya yi iƙirarin "Armée de l'air" Potez 63 jirgin sama mai injin guda biyu da aka harba. A cikin wannan gamuwa, Messerschmitt Bf 109 E ya lalace, wanda ya haifar da saukowa kusa da Cambrai. A ranar 15 ga Yuni, I. ((Jagd) "Gruppe" ya koma Saint-Omer, babban birnin kasar.
An sanya hannu kan yarjejeniyar armistice a ranar 22 ga Yuni, wanda ya kawo karshen yakin Faransa a ranar 25 ga Yuni. An ba wa rukunin hutun kwana uku, an tura wasu matukan jirgin a kan izinin gida. A ranar 30 ga Yuni, I. ((Jagd) "Gruppe" ya yi tsere don tsayar da jirgin sama na Bristol Blenheim na Royal Air Force wanda ya haifar da fada a kudu maso yammacin Saint-Omer. A cikin wannan gamuwa, Clausen ya yi ikirarin Blenheim daga No. 110 Squadron ya harbe shi wanda ba a tabbatar da shi ba amma shi kansa ya harbe shi a cikin Bf 109 E. Clausen ya sami lambar yabo ta Iron Cross 1st Class () a ranar 4 ga Yuli 1940 kuma an daukaka shi zuwa "Oberleutnant" (laftanar farko) a ranar 1 ga Fabrairu 1941. A wannan ranar, an kuma nada Clausen "Staffelkapitän" (shugaban rundunar soji) na 1. "Staffel" na "Jagdgeschwader" 77 (JG 77 <unk> 77th Fighter Wing) a ranar 6 ga Janairu 1942.