Seventy years after Thomas Jefferson penned the Declaration of Independence the United States went to war with Mexico—our first foreign war. This war did not begin suddenly; there was no Pearl Harbor. Rather, events from many years previous had sown the seeds for this conflict. Beginning in the early 1820s, Mexico allowed Moses Austin and his son Stephen to bring large numbers of Americans into its northern province of Texas. The new Mexican republic could not get its own citizens to settle in Texas, but it needed to have the area populated as a buffer against both Indian depredations...

With the existence of a state of war between the Republic of Mexico and the United States, the most pressing problem became how to raise the strength of the army to a level necessary to ensure victory. Well before the commencement of actual hostilities, authorities in the War Department gavesomethought to the need for more troops. During the last week of August 1845, the secretary of war requested the cooperation of the governors of the western states in supplying troops to Major General Taylor, should the need arise. Taylor, however, was only to call upon the governors in...

The enthusiasm with which young Americans hurried to join the army made it easy for the government to attain its manpower quotas. But before these thousands of eager recruits could actually face the enemy the army had to make sure that it trained its soldiers and provided them with the proper types and amounts of equipment, such as weapons, ammunition, food, medical supplies, tents, and blankets. This had not been a difficult task before the outbreak of war with Mexico. The army was small, less than seventy-four hundred officers and men, but suddenly the secretary of war was calling for...

Sickness began thinning the ranks of the soldiers even before they left their home states and continued as they made their way to Mexico. But after reaching their destination, their health declined precipitously. Diarrhea, malaria, and dysentery were the most pervasive diseases, but other killers such as smallpox, cholera, and yellow fever also appeared in the camps. Even such illnesses as mumps and measles proved fatal to many. Disease, which killed almost eleven thousand American soldiers and led to the discharge from service of several thousand more, was Mexico’s greatest ally in this war. In fact, the death rate of...

In the summer of 1845, John L. O’Sullivan, editor of theDemocratic Review, coined a term with which the Mexican War would forever be linked. He wrote that it was America’s “manifest destiny to overspread the continent allotted by Providence for the free development of our yearly multiplying millions.” Although the phrase “manifest destiny” was new, the idea behind it was not. As early as 1801, Thomas Jefferson had envisioned a time when citizens of the United States would spread over all of North and South America. A few years later, John Quincy Adams expressed the same sentiment, but in...

One of the major adjustments facing the volunteers as they got to Mexico was the humdrum of everyday military life. Even considering the living standards of the 1840s, most of these men left more comfortable surroundings than they were likely to find in the tent camps and garrisons in Mexico. A few took to army life with enthusiasm. A Georgian wrote his wife, “As I become acquainted with Camp duty I become more fond of the Army—it is a pleasant life—this will not be pleasant news for you.” A New Yorker agreed when he wrote of how he...

Sometimes the ways by which American soldiers in Mexico sought to relieve the boredom of camp life resulted in infractions of military regulations. Even though most of the soldiers were not bad men, some had been misfits in civilian society and continued to be troublemakers and lawbreakers in the army. These individuals faced the army’s elaborate justice system and risked a wide range of penalties. Military courts handed down sentences that varied from mere reprimands to death.

Between these two extremes was an assortment of punishments. A soldier’s punishment might be to march for several hours at a time while...

The natural inclination when thinking of war—any war—is to recall glorious scenes of the battlefield, and these are exactly the scenes to which the volunteers looked forward so eagerly. Yet the battles of the Mexican War, as in most wars, occupied only a very small percentage of a soldier’s time. During the eighteen months or so of active campaigning there were only about a dozen pitched battles. Regular troops fought the first two battles, and volunteers took part in all the rest.

Active campaigning ceased for a time following the battles of Palo Alto and Resaca de la...

Government leaders in Washington selected Col. Stephen Watts Kearny to lead a force to New Mexico. A significant trade existed between the United States and Santa Fe, and it was important that it be protected. When that area was secure, Kearny was to push on to California to assist the few Americans there. The core of his force, which came to be known as the Army of the West, would be the First U.S. Dragoons. In addition, Secretary of War Marcy requested the governor of Missouri to furnish one regiment of mounted volunteers, two companies of volunteer artillery, and two...

America’s leaders had hoped that the war with Mexico would be short. They were even optimistic that, after the battles of Palo Alto and Resaca de la Palma, the Mexican government would see the folly of continued resistance and sue for peace. Yet when Mexican authorities continued to fight even after losing Monterrey, the president and his advisers decided that the time had come to strike more directly at the heart of Mexico. Soldiers in the field also recognized the need for more drastic efforts, since Mexican leaders were unwilling to give up all the land that the United States...

Just as the British capture of Washington, D.C., in 1814 did not bring that war to a close, neither did the U.S. occupation of Mexico City effect an end to hostilities in 1847. At almost the same time that U.S. soldiers were triumphantly fighting their way past the city gates, Brig. Gen. Joaquin Rea and four thousand troops were beginning a twenty-eight-day siege of American forces in Puebla. Santa Anna himself arrived a week later to supervise matters. But in spite of the presence of the “Napoleon of the West” and the fact that the Americans were confined to three...

The American soldiers who fought in Mexico were like American soldiers in other wars in many ways. And in many ways they differed. The soldiers of the 1840s went off to war with a feeling of personal and national invincibility that was not often expressed in earlier conflicts but that American soldiers embraced avidly for the next hundred years. The soldiers of these later wars also shared a supreme confidence in their abilities to vanquish any enemy.

Those who volunteered for military service against Mexico took part in a very different kind of war than had faced their predecessors in...