The war between Mexico and the United States, in which thirty thousand soldiers from both sides were killed, broke out in 1846 and ended in 1848, but this conflict had been growing in previous years. This war was fatal for Mexico since its neighbor to the north was left with half of its territory. This territory lost it due to the expansionist pretensions of the United States. After Mexico achieved its emancipation from the Spanish crown and proclaimed itself as an independent nation, it did not achieve internal stability for many years. Mexico was undergoing independence conflicts and struggles for power in different parts of the country.

In the midst of these circumstances, Mexico faced an attack carried out by the Americans for not giving up or selling the territories located in the north of the country at that time . Next, we indicate the causes, developments and consequences of the war between Mexico and the United States.

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Causes of the United States War against Mexico

Since 1809, the United States has been carrying out different expansionist actions in order to seize different territories . By means of agreements and payments made to powers, it intended to expand its territory. It had already achieved this with the acquisition of Louisiana in 1803 and the Florida peninsula in 1819 .

After Mexico became independent , the United States set its sights on the province of Texas. Therefore, in 1825 Joel Robert Poinsett was sent in order to establish the boundaries between each country, with which the United States intended to annex the province of Texas to its territory, offering 1 million dollars for the acquisition of the territory. However, Mexico rejected such a proposal .

Yet Mexico had allowed large numbers of American immigrants to occupy Texas legally and illegally. These circumstances allowed the United States to continue to insist on obtaining the province of Texas. However, two years later, in 1827 the American government changed its strategy and offered Mexico $ 50 million for Texas , but again Mexico rejected the proposal.

Even in the midst of these circumstances, the United States remained determined to annex territories belonging to Mexico, supporting the proclamation of independence of the Mexican provinces of Texas and Alta California .

Texas Independence

A spirit of independence was developing in Texas that was unstoppable. In 1836 Texas became independent from Mexico ( see note ) . These events led to clashes between Mexican troops and the Texan independence rebels. One of the most relevant battles was the battle of San Jacinto, in which Santa Anna as military leader was captured while he slept and his entire army was caught off guard.

As a prisoner of war, President Santa Anna was forced to sign the Treaty of Velazco, which recognized Texas as an independent nation from Mexico and its border up to the Rio Grande. However, Mexico did not know the validity of the signed treaty and continued to enter Texas territory without any positive result.

Circumstances worsened when Texas was annexed as part of the United States in 1845 . Later, the Americans proposed to Mexico that the areas of New Mexico and Alta California be sold, a proposal that was rejected by the country. Consequently, Mexico broke diplomatic relations with the United States and withdrew its representative from Washington. These events gave rise to the beginning of the war between Mexico and the United States .

In 1846, American President James Polk sent troops to Texas, which were located between the Rio Grande and the Nueces rivers. On April 25, 1846, the first confrontations began between these two countries that disputed Texas and as a consequence of these confrontations, on March 13, 1846, President James Polk declared war on Mexico .

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California Independence

Colonists of American origin had occupied much of the territory of Alta California. Due to the great instability of the country, an uprising led by Californians of American origin emerged . Thus, on June 14, 1846, the Republic of California emerged . This proclamation set off alarms in the Mexican capital. Therefore, they sent troops in order to defend the northern territory.

The United States, who maintained the pretensions of taking all that territory, landed troops on the coast of Alta California where they faced Mexican military groups where they prevailed. On June 23, 1846, the commander of the US Army, John Fremont, joined his army with the Bear Flaggers , who, realizing that the United States had started war with Mexico, abandoned their plans to stabilize as an independent republic and joined the American battle lines in order to annex California to the United States.

This republic only lasted 25 days. Therefore, the proclaimed president, William B. Ide, decided to leave office and join the ranks of American soldiers. In addition, it was decided to use the American flag, thus sealing its permanence as an American state.

Development of the United States War against Mexico

After the first military confrontation between Mexico and the United States that took place in Rancho Carricitos on April 24, 1845 , the United States declared war on Mexico on May 13, 1846. Later, ten days later, on May 23, 1846, Mexico declares war on the United States .

The attacks on the Mexican nation were carried out at different strategic points in the country. There were military invasions and clashes in Coahuila, Nuevo León, Tamaulipas, Alta California, New Mexico, San Diego and Los Angeles . In addition, different ports were blocked, including: San Blas, Mazatlán, Guaymas, Frontera Carmen, Tampico, among others. The American battalions even penetrated the capital, where they hoisted the American flag .

End of the United States War against Mexico

On February 2, 1848, the Treaty of Guadalupe Hidalgo was signed. This treaty was drawn up by the Americans, known as the Mexican Secession. With the signing of this peace treaty, Mexico achieved the end of the war, but lost the territories for which it was in conflict, namely: Texas, New Mexico and Alta California . In total, Mexico lost 55% of the territory it occupied. In return, the Americans offered 3 payments in compensation for damages and expenses during the war.

Consequences of the war between the United States and Mexico

The war between Mexico and the United States resulted in the death of 16,000 Mexican soldiers and 13,283 American soldiers who lost their lives in the middle of the fighting and various diseases. In the case of Mexico, we can highlight that it received the worst portion of the conflict, it was damaged from the social by the shock of the war and its fatal victims, from the political as the instability that had been reigning since Independence and since the economic due to the enormous fiscal deficit that the war meant. Mexico was not prepared for a war of such destructive dimensions, taking into account that it faced a country that was more developed, rich, prepared and better equipped with more sophisticated weapons.

Mexico was suffering internal revolts that did not allow it to have a national and military unification against the US attack. In addition, independence movements developed in different Mexican towns. These circumstances prevented Mexico from having a large and prepared army. In addition to this, the Mexicans did not have as powerful an arsenal as that of the Americans.

In different battles they did not have enough weapons and the ones they had did not always work properly and were of less range and quality than that used by the American army. As a final consequence, Mexico lost a little more than half of the territory it occupied after achieving its independence from the Spanish empire , a territory that it could never recover.