Winfield Scott, who would ultimately be a defining military leader in the years between 1783 and 1860 - in the years between the American Revolutionary War and the Civil War - had an unpromising start to his career decades prior to the Mexican War. Historian Brion McClanahan writes:
Scott was a large man, standing six foot five and weighing around 230 pounds. He was a good student, briefly attending William and Mary College and then studying law in Petersburg, Virginia. He found little scope for his sense of adventure in a stuffy law office, and when the threat of war with the British arose in 1807, Scott immediately joined the Virginia cavalry. For the next few years, Scott bounced back and forth between the law and the army, until in 1810 he was court-martialed on trumped-up charges of making “ungentlemanly” comments about a superior officer - General James Wilkinson, a man now widely regarded as the most corrupt general in American history.
The mounting tensions in 1846 centered on land claims in the southwestern United States. Texas, which had declared itself to be independent from Mexico in 1835/1836, had fought to affirm that declaration.
Mexico begrudgingly accepted the existence of Texas as an independent republic, but when Texas joined the United States in 1845, Mexico began preparing for war.
Mexico disputed the location of Texas’s southern and western borders, and was not happy at the prospect of the United States being larger and closer to Mexico. The annexation of Texas would ensure that the United States was both.
In addition to Mexico’s wounded pride, at the thought that the Texans chose to leave Mexico and join the United States, there were also border disputes west of Texas, in New Mexico, Arizona, and California.
Polk sent diplomats to Mexico in an attempt to avoid war by paying cash for the disputed territory. The Mexican government at the time was in such disarray that the diplomats found it difficult to learn with whom they were to negotiate. Key leaders in Mexican foreign policy often held office for only a few months, and so the talks had to be restarted with different Mexican officials.
Predictably, talks broke down, and on April 25, 1846, Mexican soldiers under the command of General Mariano Arista fired on U.S. soldiers. In Washington, the Congress declared war on May 13, but, as historians Peter Maslowski and Allan Millett report,
Two major battles had already occurred. On the last day of April Arista’s army crossed the Rio Grande, and on May 8 it confronted Taylor at Palo Alto. Taylor told his men “that they main dependence must be in the bayonet,” but American artillery bore the brunt of the battle, forcing the Mexicans to withdraw. Just south of Palo Alto the open prairie gave way to dense chaparral sliced by river beds known as resacas. At Resaca de la Palma, Arista’s army assumed a strong defensive position. The tangled growth made it difficult for American artillery to deploy, and the resaca formed a natural breastwork. The battle was a melee as the chaparral shattered unit cohesion. The Mexicans again lost, fleeing across the Rio Grande. In two battles Taylor’s smaller army inflicted 800 casualties and sustained fewer than 200.
A simplified narrative of the war shows General Zachary Taylor moving southward from Texas with his army, and General Winfield Scott bringing his troops by ship southward through the Gulf of Mexico to the Bay of Campeche, landing at Vera Cruz, and fighting westward to Mexico City.
A more nuanced reading of the war includes the action of the U.S. Navy’s Pacific Squadron, under the command of John Sloat, along Mexico’s western coast and up to California; includes Col. Stephen W. Kearny leading his troops from Leavenworth, Kansas, westward to the Pacific coast in California; Col. Alexander W. Doniphan leading forces southward parallel to Taylor; General Philip Cooke leading troops from Santa Fe to California; and includes John Fremont bringing troops west to Sutter’s Fort in California and to Santa Barbara.
Of all these campaigns, Scott’s was of perhaps the greatest strategic value, while Taylor’s received the most praise in the popular press of the day. This may have been the result of Polk and Taylor conspiring to manage the war as a launching pad for Taylor’s political career. Comparing Taylor’s action to Scott’s, historian Russell Frank Weigley writes:
In the other principal campaign of the Mexican War, General Taylor showed himself to be an altogether less thoughtful and accomplished strategist than Scott. Taylor’s campaign in northern Mexico also had less strategic merit than Scott’s apart from the shortcomings of the general officer commanding. Once Taylor had secured President James K. Polk’s version of the new United States-Mexico frontier created by the American annexation of Texas, namely, the line of the Rio Grande, the strategic objects of his subsequent operations into Mexico were not clear. Too much difficult country intervened between the Rio Grande and the City of Mexico via the overland route for there ever to have existed any serious intention that Taylor should advance to the enemy capital. The American government’s hope for Taylor’s campaign of invasion across the Rio Grande into Mexico’s northern states was that occupation of those states would penalize Mexico enough to compel her to make peace, recognize the annexation of Texas, and grant the United States the other territorial increments which President Polk and his fellow expansionists desired, westward to the Golden Gate. Mexico’s northern states were so remote from the center of her national power, however, that General Scott was right to be doubtful from the beginning that Taylor’s operations could cause the Mexican government to conclude a peace satisfactory to the United States.
It might be possible to justify Taylor’s campaign by arguing that he kept Mexican troops occupied in the north so that they were unable to offer more resistance to Scott in the south. But evidence for such an interpretation is thin or nonexistent.
In any case, Scott, habitually cautious, understood the risk he took. Irving Levinson writes:
The critical phase of the conflict began when General Winfield Scott landed at Collado Beach on 9 March 1847 and marched north to the port of Veracruz and then westward to Mexico City. As he prepared to lead a force smaller than a single modern division through or near Mexican states that were home to more than 4 million people, he no doubt considered the grim threats that might be posed by a hostile populace.
Scott’s brilliant success was due not only to his own careful planning, but also to the fortunate circumstance that Mexican society was experiencing significant internal divisions at the time of the war. These divisions prevented a more efficient defense against Scott. Indeed, some factions of Mexican society were not at all supportive of the Mexican government’s war efforts, and offered no resistance to Scott whatsoever.