Kammala wannan jumla: A lokacin da aka fara yakin Mexico da Amurka a watan Yunin 1846, an sake sanya Van Buren a cikin rundunar soja a matsayin mai biyan kuɗi tare da babban majalisa. Van Buren ya yi aiki a matsayin mai taimakawa ga Janar Zachary Taylor da Winfield Scott kuma ya shiga cikin yakin Contreras, yakin Monterrey,
Siege na Veracruz, Yaƙin Cerro Gordo, da Yaƙin Churubusco.