After the northern campaign of General Zachary Taylor (1784-1850), failed to force the Mexican government to sue for peace, President James Polk (1795-1849) decided on an invasion of central Mexico with the goal of capturing Mexico City. The planning for an invasion of central Mexico was the brainchild of General Winfield Scott (1786-1866), who prepared a series of three memorandums laying out the case for the operation, which he sent to President Polk in October 1846.
Scott had desired a command of his own since the beginning of the war and he felt slighted that he had not been given command of the force in northern Mexico. Scott was suspicious that he was kept from command for political reasons since Polk was a Democrat and Scott a Whig. He was correct to be suspicious for these were exactly the reasons that Scott was denied command at the outset. General Taylor was a Democrat who was deemed politically reliable although he secretly coveted the presidency, something a successful campaign would help him achieve.
The invasion of central Mexico was planned in detail and would require twenty-thousand troops, 50 transports, and 141 flatboats to land the troops after they reached Veracruz. The flatboats were to be constructed in New Orleans and General Scott sent the Quartermaster General Thomas S. Jesup (1788-1860) to ensure they were constructed properly. In the end, only 65 boats were available for the landings due the time necessary for their construction.
The landings at Veracruz began on 9 March 1847 and on 25 March, the Mexican garrison began negotiations for surrender after taking a terrible pounding from American artillery and dismounted naval guns. The surrender was completed on 27 March, General Scott granted generous terms to the Mexicans, they were required to surrender all their arms and military equipment but the soldiers were paroled and in addition, the Americans guaranteed the security of the civilian population.
The threat of Yellow Fever, which was endemic in Veracruz, General Scott determined begin his march inland as quickly as possible. The march route would follow the National Road to Mexico City via Jalapa rather than the Orizaba road because the former was in better repair. The Mexicans were not standing still, General Antonio Lopez de Santa Ana (1794-1876) had returned to Mexico City after his defeat at Buena Vista and immediately assembled another army to oppose Scott upon learning of the surrender of Veracruz.
Santa Ana, with an army of 12,000 men met the Americans at Cerro Gordo on 18 April and was defeated; resulting in the virtual destruction of the Mexican army but Santa Ana escaped on horseback and returned to Mexico City to prepare its defenses. General Scott continued to march until he reached the city of Puebla where he was forced to stop and await reinforcements because most of the volunteer regiments in the army had completed their one year of service and wished to return home. The American army would remain in Puebla until September when sufficient reinforcements had arrived to begin the march on Mexico City.
The American assault on Mexico City began on 14 August 1847 and over the next two days; the Americans defeated all Mexican forces on the approach to the city and had effectively bottled up the Mexican army in the city itself. In order to avoid a costly attack on the walls of the city General Scott halted his army three miles outside Mexico City and offered a truce to General Santa Ana in order for armistice negotiations to begin. An armistice was concluded on 24 august but it was to be short-lived. Armistice negotiations began the next day and the both sides presented their demands. The negotiations continued until 6 September when the Mexican delegation announced that they could not acceded to the American demands and General Scott angrily terminated the armistice citing Mexican treachery.
The final assault on Mexico City began on 8 September 1847 and in a series of bloody engagements, the American forces advanced until they had captured two of the cityâ€™s gates by 14 September. As the American army was preparing for the final assault on the city itself, the mayor surrendered the city, General Santa Ana having fled the night of the thirteenth.
General Santa Ana resigned the presidency shortly after the fall of Mexico City the moderate Manuel de la Pena y Pena (1789-1850) replaced him as Mexican president. The new government began negotiations for the end of the war with Nicholas Trist (1800-1874) who had been dispatched by the President Polk with the authority to negotiate for peace.
Negotiations for a permanent peace dragged on through the Christmas holidays because of uncertainty on the part of the Mexican government. The final details were hammered out in January 1848 and a final treaty of peace was signed at Guadalupe Hidalgo on 2 February 1848, which ended the war. The United States was given the territory that makes up the states of New Mexico, Arizona, California, Nevada, and Utah in addition to paying Mexico $15,000,000 and assuming responsibility for all American claims against the Mexican government.
The campaign in central Mexico was decisive in bringing an early conclusion to the war. It is likely that if General Scott had not invaded central Mexico and captured the Mexican capital that the war would have ended very differently. General Santa Ana had shown a remarkable ability to reconstruct armies after suffering defeat. It was the capture of Mexico City that caused Santa Ana to resign the Mexican presidency, which allowed a moderate to come to power.
Brooks, Nathan C., A Complete History of the Mexican War: Its Causes Conduct, and Consequences: Comprising an Account of the Various Military and Naval Operations. From its Commencement to Treaty of Peace, Cranbury, NJ: The Scholars Bookshelf, 2006
Eisenhower, John S.D., Agent of Destiny: The Life and Times of General Winfield Scott, New York: The Free Press, 1997.
Singletary, Otis A., The Mexican War, Chicago: The University of Chicago Press, 1960
 Eisenhower, John S.D. So Far From God:Â The U.S. War with Mexico, 1846-1848, p. 253
 Ibid. p. 254
 Brooks, N.C. A Complete History Mexican War: Its Causes, Conduct, and Consequences: Comprising and Account of the Various Military and Naval Operations from its Commencement to the Treaty of Peace. First published in 1849, reprinted by: Cranbury, NJ: The Scholarâ€™s Bookshelf, 2006, pp. 310-312
 Singletary, Otis. The Mexican War, p. 93