Rubuta ci gaba ga wannan sakin layi - A lokacin yakin Mexican-American, Leonard Ross ya ba da gudummawa a cikin 4th Illinois Volunteer Infantry Regiment, ya shiga cikin Yuni 1846. An ci gaba da shi daga matsayi na sirri zuwa na farko a ranar 4 ga Satumba, 1846, ta hanyar kwamandan kwamandan, Kyaftin Lewis W. Ross, ɗan'uwansa. A cikin wasika zuwa ga matarsa, Kyaftin Ross ya lura cewa Leonard "yana jin daɗin girmamawarsa sosai & zai zama kyakkyawan jami'i. Ya rasa mutunci [sic] wanda nake ba shi da sauri kamar yadda zai yiwu daga rarar da nake da shi na labarin a hannu. " Leonard Ross daga baya ya taka muhimmiyar rawa a cikin yaƙe-yaƙe da yawa, gami da Siege na Veracruz
da kuma yakin Cerro Gordo. Bisa ga bayanin da aka rubuta a kan takarda da Kyaftin Ross ya sanya hannu da kuma ranar 30 ga Afrilu, 1847, Lieutenant Ross ya aika da murabus dinsa a wannan kwanan wata kuma ya riga ya koma gida daga yakin. Koyaya, an kuma lura da shi ta Kyaftin Ross cewa ba a karɓi murabus ɗin Laftanar Ross ba, don haka a hukumance an ɗauke shi a matsayin ba ya nan ba tare da izini ba, kodayake a bayyane yake babu wani mummunan sakamako. Ƙungiyar Tarihi ta Jihar Iowa ta ba da cikakken bayani game da aikin Leonard Ross a lokacin Yaƙin Amurka da Mexico.