Tuhia he tohutoro mō tēnei wāhanga - Ahakoa ko ia te tino rangatiratanga o tōna akomanga, i puta a Maxey i te tau 1846 ā, i whakawhiwhia ki a Brevet hei tuarua. I whakawhiwhia ia ki te 7th Infantry Regiment, i uru ki te Pakanga Mexico-American. I uru a Maxey ki te ope taua i Monterrey, Mexico. I whakahuatia a Maxey mo te maia me te rangatira tuatahi mo ana mahi i nga pakanga o Cerro Gordo me Contreras i te raumati o te tau 1847. I uru hoki ia ki nga pakanga o Churubusco
me te Molino del Rey. I whiwhi ia i te whakatipu rangatōpū, ā, i whakanohoia ia hei rangatira o tētahi kamupene pirihimana i Mexico City.