Rubuta ci gaba don wannan sakin layi - A lokacin yakin Monterrey a ranar 21-24 ga Satumba, 1846, an sanya batirin Duncan ga brigade na Thomas Staniford a cikin rukunin William J. Worth. Taylor ya kai hari kan birnin daga arewa, yayin da ya aika da sojojin Worth don kai hari daga yamma. Batirin Duncan da William W. Mackall sun shiga cikin kama fadar Bishop a ranar 22 ga Satumba. Duncan ya kasance mai kula da kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan kwamandan. A farkon Janairu 1847, an umurci Taylor da ya canja wurin Worth da Twiggs da ƙungiyoyi biyu, ciki har da Duncan, ga sojojin Winfield Scott. Duncan ya yi yaƙi a Siege na Veracruz
a ranar 9-29 ga Maris, 1847, a yakin Cerro Gordo a ranar 17 ga Afrilu, 18 ga Afrilu, da kuma wani rikici a Amazoque a ranar 14 ga Mayu.