Kammala wannan magana: Bayan barkewar yakin duniya na daya ya jagoranci rundunarsa zuwa yankin Loraine a Yammacin Yamma. A ranar 9 ga Oktoba 1914, ya zama kwamandan rundunar sojojin I a Lithuania, inda sojojinsa suka yi adawa da dakarun Rasha da suka fi yawa. Bayan rashin nasarar da aka samu na farko Kosch da mutanensa a karshe sun ci nasara a karo na biyu na Masurian Lakes. Don wannan nasarar Kosch an ba shi lambar yabo ta Pour le Mérite. A ranar 11 ga Yuni 1915 an nada shi Babban Kwamandan Janar na X. Reserve Corps. Ya jagoranci su a cikin fadace-fadace a kan Dniester, da
Yaƙin Gnila Lipa da kuma Krasnostaw. An canja shi zuwa filin wasan Balkans, inda ya yi yaƙi da Serbia. Don nasarar da Kosch ya samu, a ranar 27 ga Nuwamba, 1915, Oak Leaves zuwa Pour le Mérite.