 Ramba uchinyora ndima iyi - Paakapedza kudzidza kuWest Point, Garnett akapiwa chinzvimbo chokuva lieutenant wechipiri mu4th U.S. Artillery muna July 1841. Akapedza gore ari kuNorthern Frontier panguva yeCanada Border Disturbances, achishanda muBuffalo neFort Ontario muNew York asati apiwa basa rekugara paFort Monroe kumusha kwake Virginia. Muna 1843 Garnett akava mubatsiri wezvidzidzo paWest Point asati ava mushandi wehondo uyezve Aide-de-camp kuna General John E. Wool. Garnett akashanda muhondo yeMexico neAmerica pasi paZachary Taylor uye akagamuchira zvikwangwani zviviri zvebasa rakasiyana, rimwe paHondo yeMonterreyuye imwe nokuda kweKufamba Kwakashinga uye Kunokosha muHondo yeBuena Vista. 