Rubuta ci gaba ga wannan sakin layi - An ayyana yakin a watan Yulin 1914 kuma a ranar 5 ga Maris, 1915, kafin ya iya kammala karatun likitancinsa, Kostja Zetkin ya shiga soja. Ya yi aiki a matsayin jami'in likita a Yammacin Yamma, ya shiga cikin yakin Somme, a Verdun kuma, daga baya, a Rheims
Ka yi haƙuri. Ya ci gaba a matsayin jami'in likita ta hanyar gabatarwa da yawa, kuma an ba shi lambar yabo ta Iron Cross (Class II) a ranar 10 ga Nuwamba 1916. Bayan yaƙin ya ƙare a 1918 ya ci gaba da karatun likitancinsa, ya wuce jarabawar likitancinsa a 1923 tare da bambanci.