Kammala wannan jumla: An ba Garland mukamin Laftanar Kanar na 4 na Rundunar Sojojin Amurka a ranar 7 ga Mayu, 1839. Ya yi yaƙi a ƙarƙashin Zachary Taylor a yakin da aka yi a
Palo Alto da kuma Resaca de la Palma. A wannan lokacin ya umurci mataimakin mataimakin U.S. Grant. Don ayyuka a cikin wadannan fadace-fadace guda biyu, an ba shi izini ga cikakken kwamandan kuma ya umurci brigade na yau da kullum a cikin sashen David E. Twiggs na Army of Occupation. A yakin Monterrey, Garland na ɗan lokaci ya jagoranci rukunin a farkon harin da aka kai kan garin yayin da Janar Twiggs ya sha yawan maganin laxative kafin yakin.