Kammala jumla mai zuwa: Corbett yana da shekaru 18 lokacin da Yaƙin Duniya na Farko ya ɓarke; ya sami kwamiti a cikin Ayrshire Yeomanry kuma ya tafi tare da su zuwa Gallipoli a watan Oktoba 1915. Ayrshires na daga cikin sojojin da aka kwashe a karshe kuma suka tafi daga can zuwa Masar, suna daga cikin ragowar sojan doki a Yaƙin Gaza na Biyu. Daga nan aka tura shi zuwa Grenadier Guards; bayan sake horar da shi an tura shi zuwa Yammacin Yamma a watan Maris na 1918, ya shiga cikin Battalion na 1 a Mercatel a matsayin laftanan. Wannan ya yi daidai da hare-haren Spring na Jamus (
Operation Michael), kuma ba da daɗewa ba rundunar ta shiga aiki. A Boyelles a ranar 30 ga Maris, 1918, Corbett ya yi ƙoƙari ya tono wasu sojoji da suka ji rauni waɗanda aka binne da bindigogi, yayin da "a ƙarƙashin wuta mai ƙarfi da kuma cikakken hangen nesa na abokan gaba" kuma an ba shi Gicciye na Soja amma ya sami raunin kafa wanda ya bar shi da nakasa na dindindin.