Ka dib markii uu ka gudbay Rio Grande, bishii September Taylor wuxuu khasaare badan u geystay reer Mexico dagaalkii Monterrey, wuxuuna qabsaday magaaladaas seddex maalmood gudahood, in kasta oo ay ahayd mid aan la qabsan karin. Taylor waxaa lagu dhaleeceeyay inuu saxiixay xabad joojin "liberal" ah, halkii uu ku cadaadin lahaa is dhiibid ballaaran. Polk wuxuu rajaynayay in qabsashada Waqooyiga Mexico ay ku dhiirrigelin doonto dadka reer Mexico inay iibiyaan Alta California iyo New Mexico, laakiin dadka reer Mexico weli ma aysan rabin inay ka qeyb qaataan dhul aad u badan. Polk wuxuu ciidan u diray Winfield Scott si ay Veracruz u qabsadaan
, oo ah magaalo muhiim u ah dekeda Mexico, halka Taylor lagu amray in uu sii joogo meel u dhow Monterrey. In badan oo kamid ah askarta khibrada leh ee Taylor ayaa la hoos geeyay amarkii Scott, taasoo ka dhigeysa in Taylor uu leeyahay ciidan yar oo aan waxtar lahayn. Jeneraalka reer Mexico Antonio López de Santa Anna wuxuu qabtay warqad ka timid Scott oo ku saabsan ciidanka yar ee Taylor, wuxuuna u dhaqaaqay woqooyiga, isagoo damacsan inuu burburiyo ciidanka Taylor ka hor inta uusan la kulmin ciidanka Scott.