What Polk's intentions were regarding Mexico—and whether he even had any clear notion of what he wanted and how to get it—are a bit of a mystery even today. Texas was already a state, and while its southern boundary was a matter of dispute, no one but the Texans themselves thought it worth a war. That is why most historians believe that Polk really aimed from the start at the richest prize left in North America: the derelict province of Alta California.
Walter A. McDougall, 19971
In October 1845, the Mexican government stated it would receive a U. S. representative to negotiate outstanding differences. In response President Polk sent John Slidell, a Spanish-speaking politician from Louisiana, to Mexico. Polk instructed Slidell to negotiate the purchase of Alta California and New Mexico.
In a sense, Slidell’s mission was doomed before it started, since he was not authorized to negotiate on the two points that Mexicans felt it was necessary to discuss: 1) whether Mexico still had any residual claims to Texas; and 2) if it did not, what the boundary between Texas and Mexico was. An additional factor dooming his mission was his arriving with the title of “minister,” the equivalent of a diplomat arriving today with the title of “ambassador.” That title implied that Mexico and the United States had reestablished diplomatic relations—broken after the 1845 U. S. annexation of Texas—and that the Texas question was behind them. This view that contrasted sharply with the Mexican perception of relations with the United States.2
In his 1844 State of the Union Address, President Tyler had addressed the first point, noting that Mexico’s claim to Texas was extinguished because Texans had organized themselves into an independent republic recognized by several of “the leading powers of the earth” and because Mexico had failed to reconquer Texas after nine years.3
The U. S. claim to Texas was much stronger than its assertion that the Rio Grande formed Texas’s southern border. Slidell’s instructions on that question stated, “In regard to the right of Texas to the boundary of the del Norte [Rio Grande], from its mouth to the Paso, there cannot, it is apprehended, be any very serious doubt.”4
The U. S. claim to the Rio Grande boundary was based on: 1) the claim the United States had obtained via the Louisiana Purchase, and 2) the December 1836 claim by the Texas Congress that the Rio Grande formed the border. The Adams—Onis Treaty extinguished whatever rights might have been acquired via the Louisiana Purchase. The claim by the Texas Congress neither reflected the historic boundary of Texas nor the de facto situation during the existence of the Republic of Texas. Even after the U. S. annexation of Texas, Mexicans continued to collect customs duties at Point Isabel (today’s Port Isabel), north of the Rio Grande.5
At the time Texas was annexed to the United States, many viewed the Rio Grande as a promising trade route to New Mexico. Some Texans hoped the Rio Grande would replace the Santa Fe Trail.
Anglo settlers compared the Rio Grande to the Hudson and the Mississippi. Traders were aware that Matamoros served as a port for San Luis Potosi and other parts of northern Mexico. While the commercial and residential center of Matamoros was on the south side of the river, the actual port was just north of the mouth of the Rio Grande at Point Isabel. Control of land north of the Rio Grande would give control of the port. In fact, soon after the Mexican—American War, the port was handling $10 to $14 million worth of cargo a year. In addition to desiring the area between the Nueces and the Rio Grande for its port, ownership of this land became a matter of national pride for both countries.6
On November 30, 1845, Slidell arrived in Mexico. His instructions to acquire additional Mexican territory conflicted with Mexican nationalism. There is no indication Slidell foresaw this difficulty. He shared Polk’s view that the matter would be simple. Mexico was bankrupt, impotent, and isolated. Seemingly the easiest solution for both parties would be for Mexico to sell California, recognize the annexation of Texas, and use the money received to resolve its problems.
The Mexicans had a very different view of the situation. They felt threatened by a nation that they had seen steal land from Indians and enslave blacks and whose citizens were marching inexorably toward Mexico. The Mexicans did not share the U. S. notion that frontiersmen were the noble precursors of civilization. Rather, they saw them as barbaric, shiftless wretches who paved the way for more sophisticated operators. Many felt that if they did not take measures to stop U. S. expansion, the Mexican nation would cease to exist.7
Since Polk instructed Slidell to purchase additional territory at a time when Mexicans felt the most pressing issue was Texas, a final chance for peace was lost. To further complicate matters, Mexican firebrands were more than ready to oust any government that could be considered as kowtowing to the Americans. Any Mexican government that simply accepted the Texas question as settled and then negotiated further territorial loss, in keeping with Slidell’s instructions, would have set itself up for a coup. As historian Karl Schmitt commented: “Could any regime, administration, or leader have surrendered Texas, and then survived to make it stick? It seems highly unlikely.”8
Since Mexico had threatened to go to war if Texas was annexed, the United States was preparing its military option while Slidell was in Mexico. In 1844, a force commanded by General Zachary Taylor, who had already made a reputation as an Indian fighter, was assembled at Fort Jesup, just east of the Sabine River in Louisiana. On June 15, 1845, Taylor received orders to move southwest so that he could “protect what, in the event of annexation, will be our [south] western border.”9
In response to this order, Taylor moved his troops to Corpus Christi, a small Mexican village of fewer than a hundred people located on the Gulf Coast. An American trading post there sold goods to Mexican smugglers. Taylor’s dragoons came overland via San Antonio. Most of the rest of his men came by steamship from New Orleans. There followed six months of boredom interspersed with drills, parades, and breaking horses.10
Whether Polk wanted war, or simply wanted to negotiate from a position of strength, has been disputed since by historians. It is not an either-or question, though, since, as Polk’s biographer Charles Sellers noted, Polk thought peaceful coercion would get him what he wanted. However, if it did not, he would “not shrink from war to accomplish his purposes.”11
Events in Mexico made it appear that war could still be avoided. Despite his bellicose statements, President Paredes took no action, since he lacked an effective army and the money to finance one. Eventually, after harsh criticism in the press, he sent troops north under the command of General Pedro Ampudia. They reinforced the Mexican position on the lower Rio Grande, but did not cross to the north side of the river.12
If the Polk administration intended only to bluff the Mexicans, it pushed the situation too far. On January 13, 1846, after receiving word that Mexicans were unwilling to negotiate other matters before settling the Texas question, Secretary of War William Marcy ordered Taylor to move his force to “positions on or near” the Rio Grande.13
Taylor received his orders on February 3, 1846. After scouting the area, he began to move his forces on March 8. Taylor’s 4,000 men represented half of all U. S. army forces since at the time the United States did not feel it necessary to maintain a large standing army. Taylor assembled the largest U. S. force since the War of 1812.14
Regardless of whether Mexicans considered Texas to still be a part of Mexico, the virtually unanimous opinion in Mexico was that the State of Tamaulipas extended north to the Nueces River. In this light, Mexicans viewed Polk’s actions as an invasion, or a provocation, or both. Mexicans were not the only ones to consider Taylor’s move a deliberate provocation. Ulysses S. Grant, who served as a lieutenant in the war, wrote in his memoirs, “We were sent to provide a fight, but it was essential that Mexico should commence it.” Polk, however, said troops were ordered into the disputed territory due to the “urgent necessity to provide for the defense of that portion of our country.”15
As U. S. troops reached the north bank of the Rio Grande across from Matamoros, Mexican cotton farmers living there fled to the south side. In the U. S. Senate, anti-slavery Ohio Senator Thomas Corwin commented that Mexicans successfully grew cotton there without slaves. By Mexican reckoning, the land they farmed on the north side of the river did not lie in Texas, but in the Mexican state of Tamaulipas.16
In mid-April, General Ampudia demanded that Taylor withdraw his troops from south of the Nueces, threatening war if he failed to. Taylor replied that his orders would not permit a withdrawal.17
Taylor not only refused to withdraw, claiming that boundary problems should be left to diplomats, but he took at face value General Ampudia’s statement that his failure to do so would bring about a state of war. He ordered the mouth of the Rio Grande to be blockaded. This forced Ampudia to either withdraw or attack, since he depended on supplies brought in by ship from New Orleans. The blockade, which began April 12, was the first act of war in what is now known as the Mexican—American War.18
On April 4, in response to what Mexicans considered an invasion and to Taylor’s refusal to withdraw, Minister of War and Marine General Jose Maria Tornel ordered an attack on U. S. forces along the Rio Grande.19
On April 26, Taylor ordered an eighty-man detachment of the Second Dragoons to investigate a report that Mexican troops had crossed to the north side of the Rio Grande upstream from his position. The 1,600 Mexican soldiers who had indeed crossed the river then ambushed the detachment fifteen miles upstream from present-day Brownsville, Texas, killing or wounding seventeen Americans and taking the rest prisoner.20
Taylor wrote to Washington the next day, “Hostilities may now be considered as commenced.” His message arrived in Washington on May 9, leading Polk’s cabinet to unanimously vote to support a declaration of war. In fact, before he received news of the attack, as he recorded in his dairy, Polk had already decided to request a declaration of war based on Mexico’s failure to negotiate with Slidell, its unwillingness to sell land, its failure to resolve matters concerning Texas, and its failure to meet claims made against the Mexican government by U. S. citizens. The claims resulted from repudiated bonds, revoked concessions, and damage to American-owned property during civil strife. These claims were, Mexicans felt, a hodgepodge of reasonable demands, exaggerated claims, and the absurd. Just as was the case in the Pastry War, the failure to resolve claims was regarded as a major provocation.21
Polk reworked his already partly written war message and, on May 11, submitted it to Congress, noting that Mexicans had “shed American blood on American territory.” In addition to simply assuming that “American territory” extended to the Rio Grande, Polk rewrote history when he stated, “It is absurd for Mexico to allege as a pretext for commencing hostilities against the United States that Texas is still part of her territory.” It was the U. S. occupation of the area between the Nueces and the Rio Grande, not Mexico’s claim to Texas, that led to war.22
Paredes stated his motives for not accepting U. S. occupation of this area:
The defense of Mexican territory which the troops of the United States are invading is an urgent
Necessity, and my responsibility before the nation would be immense if I did not order the repulse
Of forces which are acting as enemies; and I have so ordered.23
Since not all members of the U. S. Congress favored war with Mexico, the declaration of war was included with the same bill that appropriated funds to support Taylor’s force. Those voting against a declaration of war also voted to deny support for American forces under attack. This was likely unnecessary, since the declaration of war passed overwhelmingly. Only fourteen of the 188 votes cast in the House, all of them by abolitionist Whigs, were against the declaration. In the Senate, the declaration passed by a vote of forty to two, with three abstentions.24
If, in fact, Polk was trying to provoke a war, he was successful. If his goal was brinkmanship, he failed due to: 1) his acceptance at face value of Mexicans’ bellicose statements, which were demanded by the Mexican public, 2) considering Slidell’s rejection frivolous, without realizing how delicate Paredes’ position was, and 3) defining as settled the border between Texas and Mexico.
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