Rubuta ci gaba don wannan sakin layi - A lokacin Yaƙin Duniya na Farko Mangin ya tashi daga kwamandan rukuni zuwa na Sojoji na Goma don Yaƙin Marne na Biyu, yana jagorantar sojojin Faransa da na Amurka. An yi wa lakabi da "The Butcher" saboda amincewarsa da "la guerre à outrance" (yaƙin gaba ɗaya) da kuma imaninsa game da dacewar Arewacin Afirka Tirailleur don kai hari, babu shakka a cikin sojojin Faransa cewa Mangin ba shi da tsoro. Ba kamar sauran janar-janar na Faransa da ba su ziyarci gaba ba, an harbe Mangin a kirji yayin da yake karfafawa mutanensa don ci gaba da kai hare-hare a lokacin Yaƙin na biyu na Champagne, kodayake ya koma aiki bayan kwana goma. A lokacin wannan yaƙin, Mangin ya sami nasarori masu ban mamaki a yakin Charleroi
a 1914 sannan a yakin Verdun a 1916 amma sunansa ya sha wahala bayan bala'in Nivelle Offensive (16 ga Afrilu <unk> 9 ga Mayu 1917). Wannan ya faru ne saboda gaskiyar cewa Mangin yana daya daga cikin manyan jami'an Faransa da suka goyi bayan dabarun Nivelle.