“Monterrey is ours,” wrote U.S.  Army lieutenant Napoleon Dana to his wife Sue in September 1846.  “I can hardly describe to you with my pen what difficulties, dangers, and labors we have gone through to gain it.” Lieutenant Dana had just survived four days of intense fighting as American troops captured the Mexican city of Monterrey.

“The enemy fought very obstinately here, and we had to fight them by inches and advance upon them from house to house. ...  Soon after dark our mortar began to fire. ...  The shells all burst beautifully right in the plaza, scattering death and devastation.”

Dana and other American troops remained in the city for two months, taking over the houses of wealthy residents.  The army assigned Dana to the home of “one Don Manuel Somebody.” He wrote Sue of beautiful palace grounds “such as you may have seen in pictures of Italian gardens in older times.” In mid-December, the night before leaving Monterrey, he paid a farewell visit to Don Manuel, whom he now regarded as a “right good old fellow.” As the elderly Mexican said goodbye, he made “a long and affecting speech ... while his eyes filled. ...  He said that if the war continued, he foresaw nothing but the ruin of his native land.”

The stage had been set for war with Mexico years before.  Territorial disputes between the United States and its southern neighbor began as far back as 1803, when the United States claimed Texas as part of the Louisiana Purchase.  The United States renounced that claim in the Adams-Onís Treaty of 1819, but the idea of Manifest Destiny and of acquiring Mexican territory had strong popular support.

Tensions grew during the administration of John Tyler, who hoped to bring Texas into the Union.  Because Texas already possessed a significant population of Southerners who had taken enslaved African Americans into Texas, it was certain to support the cause of slavery.  Antislavery leaders in Congress therefore opposed annexation.  Moreover, Mexico had never recognized the independence of Texas and still considered it Mexican territory.

Analyze:
Why did antislavery members of Congress oppose admitting Texas to the Union?
 

Texas and Oregon Enter the Union

In early 1844, after spearheading a publicity campaign in favor of annexation, President Tyler brought the matter before the Senate.  He blundered, however, by including in the supporting documents a letter written by Secretary of State John C.  Calhoun that contained a fierce defense of slavery.  Outraged Northerners pointed to the letter as evidence that annexation was nothing but a pro-slavery plot, and by a count of 35 to 16, the Senate voted against annexation.  The maneuver that Tyler believed would win him a second term instead destroyed his chances of retaining the presidency.

The Election of 1844

As the presidential race began later that year, the front-runners for the nomination were Whig senator Henry Clay and former Democratic president 
Martin Van Buren.  Although politicians on both sides of the annexation issue pressed the candidates to state their positions, both responded cautiously to avoid losing supporters.

Van Buren’s indecision cost him the Democratic nomination.  His party instead chose James K.  Polk, a former Congressman and governor of Tennessee.  Polk promised to annex not only Texas but also the contested Oregon territory in the Northwest.  In addition, he vowed to buy California from Mexico.  The ambitious platform appealed to both Northerners and Southerners because it expanded the country while promising to maintain the delicate balance between free and slave states.

The Democrats’ unity on annexation caused Clay to backpedal.  Reversing a statement made in the spring of 1844 against immediate annexation, Clay now supported annexation of Texas as long as it was done without causing war with Mexico.  This so angered antislavery Whigs in his party that they threw their support to the Liberty Party—a small third party that supported abolition.  With the Whig vote split, Polk won the election.

The Oregon Question

In public, Polk took a strong stance on Oregon.  Despite British claims on the region, he said that the United States had a “clear and unquestionable” right to it.  His supporters cried “Fifty-four Forty or Fight,” declaring that they wanted all of Oregon to the line of 54° 40’ north latitude.

In private, however, Polk agreed to split the territory.  In June 1846 Great Britain and the United States resolved the dispute.  The United States received all of Oregon south of 49° north latitude, except for the southern tip of Vancouver Island.

The Annexation of Texas

Even before Polk took office, outgoing president Tyler pushed an annexation resolution through Congress in February 1845.  The resolution succeeded because it needed only a simple majority of both houses rather than the two-thirds majority needed to ratify a treaty.  Texas joined the Union in 1845.  Mexico was outraged and broke diplomatic relations with the U.S.  government.  Matters worsened when the two countries disputed the location of Texas’s southwestern border.  Mexico said it was the Nueces River.  Texans, and then the United States, claimed the Rio Grande, about 150 miles (240 km) farther west and south, as the boundary.  The Texas-United States claim covered far more territory than the Mexican claim, including some of what is now eastern New Mexico.

Polk’s intentions in California added to the growing strife.  In November 1845 he sent John Slidell as special envoy, or representative, to Mexico City to try to purchase the territory.  Mexico’s new president, José Joaquín Herrera, refused even to meet with Slidell.

Different Viewpoints

Did Manifest Destiny Violate American Ideals?

In the 1800s, many Americans believed the United States was destined to reach from the Atlantic Ocean to the Pacific Ocean.  This national mission also implied that Americans were superior to their neighbors who also controlled territory in North America.  Did this belief in American superiority contradict the spirit of equality important to so many Americans?

Public servant Albert Gallatin opposes Manifest Destiny:

At the age of 86, after a distinguished career in public service, Albert Gallatin became president of the New York Historical Society.  The war against Mexico revived his interest in politics, and he wrote:

“It is said that the people of the United States have a hereditary superiority of race over the Mexicans, which gives them the right to subjugate and keep in bondage the inferior nation. ...  Is it compatible with the principle of democracy, which rejects every hereditary claim of individuals, to admit a hereditary superiority of races?

...  Can you for a moment suppose that a very doubtful descent from men who lived 1,000 years ago has transmitted to you a superiority over your fellow men? ...  At this time the claim is but a pretext for covering and justifying unjust usurpation and unbounded ambition.

...  Among ourselves the most ignorant, the most inferior, either in physical or mental faculties, is recognized as having equal rights, and he has an equal vote with anyone, however superior to him in all those respects.  This is founded on the immutable principle that no one man is born with the right to governing another man.”

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Editor John L.  O’Sullivan supports Manifest Destiny:

John L.  O’Sullivan first used the phrase “manifest destiny” in a July 1845 edition of the United States Magazine and Democratic Review.

In the following article excerpt, he promotes the spread of democracy:

“Texas is now ours.  Already, before these words are written, her convention has undoubtedly ratified the acceptance, by her congress, of our proffered invitation into the Union. ...  Her star and stripe may already be said to have taken their place in the glorious blazon of our common nationality. ...  The next session of Congress will see the representatives of the new young state in their places in both our halls of national legislation, side by side with those of the old Thirteen.

Why ... [have] other nations ... undertaken to intrude themselves into [the question of Texas]?  Between us and the proper parties to the case, in a spirit of hostile interference against us, for the avowed object of thwarting our policy and hampering our power, limiting our greatness and checking the fulfillment of our manifest destiny to overspread the continent allotted by Providence for the free development of our yearly multiplying millions.”

The War With Mexico

Herrera’s snub ended any realistic chance of a diplomatic solution.  Polk ordered troops led by General Zachary Taylor to cross the Nueces River—in Mexico’s view, an invasion of its territory.  Polk wanted Mexican soldiers to fire the first shot.  If he could say Mexico was the aggressor, he could more easily win popular support for a war.

Finally, on May 9, 1846, news reached him that a force of Mexicans had attacked Taylor’s men.  In an address to Congress, Polk declared that the United States was at war “by the act of Mexico herself.” Hoping to incite the public’s indignation, he added that “American blood has been shed on American soil!”

Many Whigs opposed the war as yet another plot to extend slavery.  Most Washington politicians, though, recognized that however questionable Polk’s actions, the United States was committed to war.  On May 13 the Senate voted 40 to 2 and the House 174 to 14 in favor of the war.

Calling All Volunteers

Polk and his advisers developed a three-pronged military strategy.  Taylor’s troops would continue to move south, crossing the Rio Grande near the Gulf of Mexico.  A separate force to the northwest would capture Santa Fe, an important trading center in what is now New Mexico, and then march west to take control of California with the help of the American navy.  Finally, U.S.  forces would advance to Mexico City and force Mexico to surrender.

To implement the ambitious plan, the United States needed to expand the army.  Congress authorized the president to call for 50,000 volunteers, and men from all over the country rushed to enlist.  Almost 73,000 answered the call.

Undisciplined and unruly, the volunteers proved to be less than ideal soldiers.  As one officer observed, “They will do well enough to defend their own firesides, but they can not endure the fatigue incident to an invading army.” Another bemoaned in a half-comical way their constant demands on his attention:
 

“[O]ne wanted me to read a letter he had just received; another wanted me to write one for him; another wanted me to send his money home; another wanted me to keep it for him. ...  [O]ne complained that his uniform was too large, another that his was too small.”

In early May, several days before Polk signed the declaration of war, Taylor’s troops defeated Mexican forces, first at Palo Alto and then at Resaca de la Palma.  Taylor then moved south, overcoming more enemy forces at Matamoros.  By late September he had marched about 200 miles (322 km) west from the Gulf Coast and captured Monterrey.

In the meantime, Colonel Stephen W.  Kearny led troops from Fort Leavenworth, west of Missouri, toward Santa Fe.  The march through the dry countryside was brutal, but when Kearny’s men reached the city in August, the Mexican force there had already fled.  With Santa Fe secured, a small U.S.  force headed on to California.

Before Kearny’s force arrived and even before war with Mexico was officially declared, settlers in northern California, led by American general John C. Frémont, had begun an uprising.  The official Mexican presence in the territory had never been strong, and the settlers had little trouble overcoming it.  On June 14, 1846, they declared California independent of Mexico and renamed the region the Bear Flag Republic.

A few weeks later, the Bear Flag Republic came to an end when naval forces of the United States occupied San Francisco and San Diego and took possession of California for the United States.

To Mexico City

The war had proceeded just as President Polk had hoped, but despite having lost vast territories, Mexico’s leaders refused to surrender.  Polk decided to force things to a conclusion with the third phase of his battle plan.  He sent soldiers on ships to the Mexican port of Veracruz, from where they would march west and capture the Mexican capital, Mexico City.

Polk, seeing Taylor as a potential rival in the 1848 election, eased him out of the war by placing General Winfield Scott, a member of the Whig Party, in command of this campaign.  In March 1847 Scott’s force landed at Veracruz.  The troops headed for Mexico City, battling the enemy along the way.  On September 14, after a hard fight, they finally captured the capital.

The Peace Treaty

After the fall of Mexico City, Mexico’s leaders could no longer hold out.  On February 2, 1848, they signed the Treaty of Guadalupe Hidalgo.  In the agreement, Mexico ceded, or gave up, more than 500,000 square miles (1,295,000 sq.  km) of territory to the United States.  This land is now the states of California, Utah, and Nevada, as well as most of New Mexico and Arizona and parts of Colorado and Wyoming.  Mexico also accepted the Rio Grande as the southern border of Texas.  In exchange, the United States paid Mexico $15 million and agreed to take over $3.25 million in debts the Mexican government owed to American citizens.

With Oregon and the former Mexican territories now under the American flag, the dream of Manifest Destiny was finally realized: the United States now stretched from ocean to ocean.  Valuable ports on the west coast opened up new avenues to the Pacific nations of Asia.  The question of whether the new lands should allow slavery, however, would soon lead the country into another bloody conflict.  The experience that such men as Robert E.  Lee and Ulysses S.  Grant gained during the war would soon be used to lead Americans against each other.

Summarize:
What was President Polk’s military strategy in the war with Mexico?
 

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