Bayan kammala karatunsa, Jefferson Davis ya yi shekaru shida a matsayin laftanar a cikin Sojojin Amurka. Ya yi yaƙi a cikin Yakin Mexico da Amurka (1846-1848), a matsayin colonel na rundunar sa kai. Kafin yakin basasar Amurka, ya gudanar da babban gonar auduga a Mississippi, wanda ɗan'uwansa Joseph ya ba shi, kuma ya mallaki bayi 113. Ko da yake Davis ya yi jayayya da rabuwa a 1858, ya yi imanin cewa yana da haƙƙin haƙƙin barin Ƙasar Mexico. Tambaya: Yaushe ne Jefferson Davis ya yi yaƙi a ƙarshen yaƙin Amurka da Amurka?
Shekara ta 1848