Per the “Conservapedia”

Background

In 1810, Mexico received its independence from Spain. In 1824, with the Mexican government wishing to settle the mostly-empty northern region, Moses Austin was invited to settle a colony of Americans in east Texas. The only conditions were that the Americans convert to Catholicism, renounce their American citizenship, become "Mexicanized," and either free or leave behind their slaves. Most of these requests were ignored, and not easily enforceable. After the death of Austin, his son Sam Austin became the de-facto leader of the Texans. The Tejanos (American residents of Texas) wished for increased trade with the United States, more self-rule, and slavery. When met with the "Napoleon of the West," the new Mexican President-General Santa Anna, by 1835, increased tensions between the central government in Mexico City and the distant region of Texas were at the brink of war.

The War

The Alamo and Goliad

Texas declared its independence from Mexico, and Santa Anna quickly raised a 6000-strong army to put down the insurrection, despite the approaching winter. Santa Anna lost hundreds of troops in the desert winter while on the march, but arrived in Texas earlier than expected. Sam Houston, a former governor of Tennessee, had been gathering volunteers to face Santa Anna. With Houston's forces still in disarray, Santa Anna laid siege to the San Antonio fortress, the Alamo. Actually an old Spanish mission, it had been hastily barricaded into an impromptu fort. 187 Texans famously held out for thirteen days despite knowing they would not be able to live through the 6,000-man assault. All 187 Texans were killed, including their commander William Travis, and other notable persons such as David Crockett and Jim Bowie. The Mexican army suffered up to 1000 casualties.

At the Battle of Goliad, a force of 300 Texans was surrounded by the Mexican army. After three costly charges, the Mexicans called in cannons and reinforcements, and surrounded the Texans in the night. The Texans surrendered the following day. At the Goliad Massacre, General Santa Anna ordered the execution of all prisoners. Despite the deaths of up to 400 Texans in these two battles, these two occurrences were vital to the Texas Revolution. These two strategically unimportant locations delayed the Mexican advance for several weeks, allowing Houston to gather much-need support in eastern Texas. Also, the martyrdom of those who willingly gave their lives at the Alamo, as well as the butchery at Goliad, galvanized the Texan cause.

Battle of San Jacinto

Santa Anna, now unhindered, marched into the heart of Texas in pursuit of Houston. Houston, who knew his small but ever-growing army still could not hope to meet the Mexicans in battle, performed a strategic retreat eastward towards the United States. Much of the Texan support was coming from the western US, and as Houston retreated, his supply lines shortened. The Mexicans, who had limited food and supplies, were lengthening their supply lines from Mexico City every day. Houston also burned the towns and fields he passed through, so as to deny the Mexican army the ability to plunder and re-supply. An unexpected split of the Mexican army occurred, in which over half of Santa Anna's forces, under the command of General Urrea (the general who had called for reinforcements on the first day at Goliad), turned towards Galveston, the temporary capital of Texas. Houston, at the demands of his 900 weary men, turned to face his enemy while he was only slightly outnumbered, with the Mexican forces now only numbering 1200.

Santa Anna, who believed that the Texans would again retreat upon realizing that they were still outnumbered, ordered his men to set up camp along the banks of the San Jacinto River. Houston's men, however, were eager to fight. Houston ordered an attack the following morning, unwittingly catching the Mexicans during their siesta hour. The unprepared Mexicans were massacred, with all soldiers being either killed or captured. The Texans lost nine. The captured Santa Anna ordered General Urrea to return to Mexico City, and granted the Texans their Independence. American President Andrew Jackson, as well as Great Britain, soon recognized the Republic of Texas as an independent nation.

 

Per the “History Guy”

The Mexican-American War was the first major conflict driven by the idea of "Manifest Destiny"; the belief that America had a God-given right, or destiny, to expand the country's borders from 'sea to shining sea'. This belief would eventually cause a great deal of suffering for many Mexicans, Native Americans and United States citizens. Following the earlier Texas War of Independence from Mexico, tensions between the two largest independent nations on the North American continent grew as Texas eventually became a U.S. state. Disputes over the border lines sparked military confrontation, helped by the fact that President Polk eagerly sought a war in order to seize large tracts of land from Mexico.

CAUSES OF CONFLICT:

The war between the United States and Mexico had two basic causes. First, the desire of the U.S. to expand across the North American continent to the Pacific Ocean caused conflict with all of its neighbors; from the British in Canada and Oregon to the Mexicans in the southwest and, of course, with the Native Americans. Ever since President Jefferson's acquisition of the Louisiana Territory in 1803, Americans migrated westward in ever increasing numbers, often into lands not belonging to the United States. By the time President Polk came to office in 1845, an idea called "Manifest Destiny" had taken root among the American people, and the new occupant of the White House was a firm believer in the idea of expansion. The belief that the U.S. basically had a God-given right to occupy and "civilize" the whole continent gained favor as more and more Americans settled the western lands. The fact that most of those areas already had people living upon them was usually ignored, with the attitude that democratic English-speaking America, with its high ideals and Protestant Christian ethics, would do a better job of running things than the Native Americans or Spanish-speaking Catholic Mexicans. Manifest Destiny did not necessarily call for violent expansion. In both 1835 and 1845, the United States offered to purchase California from Mexico, for $5 million and $25 million, respectively. The Mexican government refused the opportunity to sell half of its country to Mexico's most dangerous neighbor.

 

The second basic cause of the war was the Texas War of Independence and the subsequent annexation of that area to the United States. Not all American westward migration was unwelcome. In the 1820's and 1830's, Mexico, newly independent from Spain, needed settlers in the underpopulated northern parts of the country. An invitation was issued for people who would take an oath of allegiance to Mexico and convert to Catholicism, the state religion. Thousands of Americans took up the offer and moved, often with slaves, to the Mexican province of Texas. Soon however, many of the new "Texicans" or "Texians" were unhappy with the way the government in Mexico City tried to run the province. In 1835, Texas revolted, and after several bloody battles, the Mexican President, Santa Anna, was forced to sign the Treaty of Velasco in 1836 . This treaty gave Texas its independence, but many Mexicans refused to accept the legality of this document, as Santa Anna was a prisoner of the Texans at the time. The Republic of Texas and Mexico continued to engage in border fights and many people in the United States openly sympathized with the U.S.-born Texans in this conflict. As a result of the savage frontier fighting, the American public developed a very negative stereotype against the Mexican people and government. Partly due to the continued hostilities with Mexico, Texas decided to join with the United States, and on July 4, 1845, the annexation gained approval from the U.S. Congress.

 

Mexico of course did not like the idea of its breakaway province becoming an American state, and the undefined and contested border now became a major international issue. Texas, and now the United States, claimed the border at the Rio Grande River. Mexico claimed territory as far north as the Nueces River. Both nations sent troops to enforce the competing claims, and a tense standoff ensued. On April 25, 1846, a clash occurred between Mexican and American troops on soil claimed by both countries. The war had begun.

 

 DESCRIPTION OF CONFLICT:

The Mexican-American War was largely a conventional conflict fought by traditional armies consisting of infantry, cavalry and artillery using established European-style tactics. Such a conflict, in modern times, would require a masters in communication and heavy use of geographic information technology. As American forces penetrated into the Mexican heartland, some of the defending forces resorted to guerrilla tactics to harass the invaders, but these irregular forces did not greatly influence the outcome of the war.

After the beginning of hostilities, the U.S. military embarked on a three-pronged strategy designed to seize control of northern Mexico and force an early peace. Two American armies moved south from Texas, while a third force under Colonel Stephen Kearny traveled west to Sante Fe, New Mexico and then to California. In a series of battles at Palo Alto and Resaca de Palma (near current-day Brownsville, Texas), the army of General Zachary Taylor defeated the Mexican forces and began to move south after inflicting over a thousand casualties. In July and August of 1846, the United States Navy seized Monterey and Los Angeles in California. In September, 1846, Taylor's army fought General Ampudia's forces for control of the northern Mexican city of Monterey in a bloody three-day battle. Following the capture of the city by the Americans, a temporary truce ensued which enabled both armies to recover from the exhausting Battle of Monterey. During this time, former President Santa Anna returned to Mexico from exile and raised and trained a new army of over 20,000 men to oppose the invaders. Despite the losses of huge tracts of land, and defeat in several major battles, the Mexican government refused to make peace. It became apparent to the Polk Administration that only a complete battlefield victory would end the war. Continued fighting in the dry deserts of northern Mexico convinced the United States that an overland expedition to capture of the enemy capital, Mexico City, would be hazardous and difficult. To this end, General Winfield Scott proposed what would become the largest amphibious landing in history, (at that time), and a campaign to seize the capital of Mexico.

On March 9, 1847, General Scott landed with an army of 12,000 men on the beaches near Veracruz, Mexico's most important eastern port city. From this point, from March to August, Scott and Santa Anna fought a series of bloody, hard-fought battles from the coast inland toward Mexico City. The more important battles of this campaign include the Battles of : Cerro Gordo (April 18), Contreras (August 20), Churubusco (August 20), Molino del Rey (September 8) and Chapultepec (September 13). Finally, on September 14, the American army entered Mexico City. The city's populace offered some resistance to the occupiers, but by mid-October, the disturbances had been quelled and the U.S. Army enjoyed full control. Following the city's occupation, Santa Anna resigned the presidency but retained command of his army. He attempted to continue military operations against the Americans, but his troops, beaten and disheartened, refused to fight. His government soon asked for his military resignation. Guerrilla operations continued against Scott's lines of supply back to Veracruz, but this resistance proved ineffective.

On February 2, 1848, The Treaty of Guadeloupe Hidalgo was signed, later to be ratified by both the U.S. and Mexican Congresses. The treaty called for the annexation of the northern portions of Mexico to the United States. In return, the U.S. agreed to pay $15 million to Mexico as compensation for the seized territory. The bravery of the individual Mexican soldier goes a long way in explaining the difficulty the U.S. had in prosecuting the war. Mexican military leadership was often lacking, at least when compared to the American leadership. And in many of the battles, the superior cannon of the U.S. artillery divisions and the innovative tactics of their officers turned the tide against the Mexicans. The war cost the United States over $100 million, and ended the lives of 13,780 U.S. military personnel. America had defeated its weaker and somewhat disorganized southern neighbor, but not without paying a terrible price.