On this day, 179 years ago, May 13, 1846 (April 18, 1846 in the lunar calendar), the US-Mexico War broke out. The American-Mexico War was a war between the United States and Mexico that broke out from 1846 to 1848. Through this not-so-large-scale war, the United States seized 2.3 million square kilometers of land and became a major country across the Atlantic and Pacific Oceans, a rare sight in the world. Mexico has lost most of its territory and its vitality has been greatly damaged. The United States has since gained dominance in the Americas. Map of the U.S. -Mexico War from May 1846 to February 1848 The U.S. War against Mexico was a war of key significance in the history of continental expansion and the Western Movement of the United States. It not only promoted the formation and development of an economic power in the United States, but also intensified the contradiction between industrial capital in the north and slavery in the south, and became the precursor of the American Civil War. During the peak period of the expansion of the continental United States and the westward movement in the 1840s, the expansionist theory of "heaven determines a destiny" was the theoretical basis for the United States to launch war against Mexico. On December 2, 1845, U.S. President Polk proposed an expansionist interpretation of the Monroe Doctrine in his annual address to Congress. [The same year] On December 27, the New York Morning News published an article by expansionist O'Sullivan, saying: "The right given by God to us to develop across the continent is a destiny determined by nature"(Frederic Merck,"Destiny and the Mission in American History-A Reinterpretation"). On January 3, 1846, Congressman Robert Winthrop proposed in Congress: "Our right to determine our destiny extends to the entire continent"(Richard Morris, ed., Encyclopedia of American History). [From the time the United States planned the 'independence' of Texas in 1836 to the US-Mexico War in 1846, it ran through] The United States has a long-standing ambition to seize the California area and the Pacific Ocean outlet. In 1835, President Jackson tried to buy the port of San Francisco and the area north of it for $550,000. In November 1845, President Polk attempted to seize New Mexico and California, threatening Mexico to repay US$3 million in debt to the United States. The Mexican government rejected the unreasonable demands of the United States. On January 13, 1846, Polk ordered Taylor's troops to cross the Nuesese River and occupy the left bank of the Rio Grande River, which had never belonged to Texas. On April 25, a bloody clash broke out between U.S. and Mexican troops in Mexico. On May 8 and 9, the United States and Mexico exchanged fire in the Palo Alto and Resaca de La Palma areas [Taylor, nicknamed the "tough old man", became famous]. On the evening of May 9, the U.S. government met and decided to take war action against Mexico. [1846 On May 11, 2008, President Polk delivered a message to the Congress, calling for a declaration of war against Mexico. On the same day and the next day, the U.S. House of Representatives and the Senate respectively passed resolutions to declare war on Mexico.] On May 13, Polk issued a statement declaring that "a state of war exists" between the United States and Mexico (edited by James Richardson,"U.S. President's Address and Compilation of Documents"). On May 13, 1846, the United States declared war on Mexico, and the American-Mexican War broke out. The United States has an absolute advantage over Mexico in terms of power. The United States has a developed economy, a well-trained and well-equipped military, has advanced front-loaded rifles and artillery, and the Navy controls sea power. Mexico is a backward agricultural country with a population of 7 million, most of whom are Indians. There are only 32,000 troops in the country, almost no navy, poor equipment, and lack training and discipline. The war is roughly divided into two stages. 1846-1847 In February 2008, the battlefield mainly unfolded in three directions. Taylor commanded the main force of the U.S. military to engage the main force of the Mexican army in northern Mexico. At the Battle of Palo Alto on May 8, 2300 U.S. troops fought 6000 Mexican troops. The U.S. troops defeated the opposing cavalry with superior artillery fire. On May 9, 1700 U.S. troops defeated 5700 Mexican troops at Resaca de La Palma. On September 24, the number of U.S. troops increased to 15,000 and captured Monterey. In February 1847, the two sides fought fiercely in Buenos Vista. The commander of the Mexican army, Santana, used 20,000 troops to attempt to encircle and annihilate 5000 US troops. The Mexican army repelled U.S. attacks several times and captured more than 400 people. However, the US military relied on its artillery advantage to repel the Mexican army. In this battle, the U.S. military suffered 746 casualties and the Mexican army lost 1500 to 2000 people. In California, between June and July, American immigrants defeated the Mexican army, established the "Republic of California" and raised the "Bear Star Flag." The U.S. Navy expedites California to support immigrants. In September, Mexicans revolted and expelled American immigrants. The United States sent additional troops to cooperate with the Pacific Squadron to defeat the Mexican army in California and New Mexico and integrate these two areas into the United States. In December 1846, Donifin led 900 U.S. troops on a long-distance expedition of more than 1000 miles, captured the important town of Chihuahua in northern Mexico, and joined forces with the Taylor Army in Monterey. By the end of the first phase of the war, the United States had captured a large area of northern Mexico. Although the U.S. military was small in number, it relied on its superior tactical literacy and sophisticated equipment to defeat the dominant Mexican army, mainly Indians. The Mexican people launched a guerrilla war in the US-occupied area, forcing the U.S. military to stop its march. From February 1847 to 1848, the war entered its second phase. The number of U.S. troops increased to 60,000, half of which were sent to Mexico. In order to completely defeat the Mexican resistance, the US military changed its main direction and began to find the shortest route to capture the capital, Mexico City. U.S. Commander Winfield Scott planned and carried out the two-sided landing on Veracruz. Veracruz is the largest port on the east coast of Mexico and has important strategic value. Scott concentrated 13,000 troops, equipped with 50 cannons, and attacked the port with the support of the Navy's Gulf Coast Squadron. Veracruz is defended by 4000 Mexican troops and has strong fortifications. In order to complete the amphibious attack, Scott specially ordered special landing craft, conducted intensive training for the troops, and made careful preparations. Starting on March 9, U.S. troops began landing on a beach three miles southeast of Veracruz. The Mexican army did not resist, and the 8000 American troops landed smoothly without any casualties. Then, the US military began to siege Veracruz. Starting on March 22, 72 U.S. warships and army artillery carried out barbaric shelling on Veracruz for several days. Scott ordered that no living person would be allowed to leave the city unless the Mexicans surrendered. Under the fierce artillery fire of the U.S. military, the city was severely damaged. For a time,"blood flowed into canals on the streets of the city, and the limbs and fragments of people blown away by enemy shells fell everywhere." More than 100 civilian casualties and 5 million pesos were lost. The Mexican defenders put forward strong resistance, and dockworkers and fishermen also actively participated in the war, costing the U.S. military 82 casualties. On March 29, the Mexican army stopped resisting at the order of its commander, and the U.S. military captured the city. This amphibious landing was very successful from a military point of view. The U.S. Army, Navy and Navy worked closely together to achieve the predetermined combat goals. It was called "the most successful amphibious landing operation of the 19th century." The US military then advanced towards the capital, Mexico City. Sant 'Anna hastily gathered 13,000 people to fight the U.S. military in Serro Gordo. On April 18, the U.S. military made a surprise attack through the dense forest of the valley and raided the left wing of the Mexican army, defeating the Mexican army, capturing more than 3000 people and injuring 400 U.S. troops. On May 15, the U.S. military advanced to Puebla, 80 miles away from Mexico City. As the city's upper echelons surrendered, the U.S. military captured Mexico's third-largest city without bloodshed. On August 6, 10,000 U.S. troops arrived at the foot of Mexico City. Mexican soldiers and civilians launched a heroic battle to defend the capital. The Mexican army has gathered 20,000 people and 100 artillery pieces. At this time, the Mexican army was mainly white, and its combat effectiveness had been significantly improved. The two sides first launched a fierce battle on the outskirts of the suburbs. In the Battle of Contreras and Churobusko, the US military once again defeated the superior enemy with heavy artillery fire. More than 7000 Mexican soldiers were killed and captured, but the U.S. military also suffered nearly a thousand casualties. On September 7, the Mexican government held short-term negotiations with the United States and rejected the unreasonable demands of the United States. The U.S. military launched a general offensive on Mexico City. The Mexican army fought bravely and repelled many U.S. attacks, causing heavy casualties to the U.S. military. The fighting was particularly fierce on Mount Chapultepec, which overlooks Mexico City. Students at the Mexican Military Academy fought heroically. The US military charged towards the top of the mountain like a flood. The students braved the hail of bullets and fought back bravely. The US military suffered casualties everywhere. After the Mexican army ran out of bullets, it engaged in hand-to-hand combat with the enemy. In the end, six young students fought to the last person and sacrificed their lives honorably. They were praised as "young heroes". At dusk on September 13, Sant 'Anna led government members to retreat. The city was in chaos, and the presidential palace was also looted by rioters. At dawn on September 14, U.S. troops entered the city. At first, the US military was showing off its strength and held a city entrance ceremony wearing brand new uniforms. Many citizens watched. Suddenly, there was a loud burst of gunfire. Mexican sniper fired at the US military from all directions, and the US military fell one after another. The fierce street fighting lasted for a whole day, with more than 860 U.S. troops casualties. Later, because the Mexico City Senate was afraid of retaliation by the US military and ordered a ceasefire, the US military finally captured the Mexican capital. However, the Mexican army is still fighting fiercely with the US military across the country. The Mexican people are also launching guerrilla warfare in the US-occupied area, using machetes, spears, and shotguns to fight against the US military. In February 1847 alone, an ambush killed more than 300 U.S. troops. In October, the guerrillas raided Puebla again, killing the U.S. governor and wiping out most of the garrison. The US military carried out cruel suppression, but it was still unable to extinguish the fire of people's resistance. At the end of 1847, 20,000 U.S. troops were fighting the guerrillas. If the Mexican government could fully mobilize the people, it could have turned defeat into victory. But the upper ruling clique panicked by the fall of the capital, dismissed St. Anna from his duties in October 1847, formed a new government, and began negotiations with the United States. In February 1848, the two sides signed the Treaty of Guadalupe Hidalgo. Mexico ceded 1.9 million square kilometers of more than half of its territory, namely, the present-day American states of California, Nevada, Colorado, Texas, New Mexico and Arizona. The United States paid $18.25 million. The US-Mexico War was a naked war of aggression launched by the United States. Even American general Grant admitted that "this war was one of the most unjust wars ever waged by a strong nation against a weak nation." The war ended with the United States winning and Mexico ceding territory and seeking peace. But the United States also paid a heavy price: 12876 people died (11155 died due to internal injuries), 4102 people were injured, and a cost of US$97.5 million. The reason for Mexico's defeat was that its leaders, aristocrats and clergy, fought for power and compromised and surrendered. The Mexican army was poorly trained, backward in equipment, and poor in command by aristocratic officers. The US military is victorious in that it has good military quality and absolute advantages in tactical level, firepower and mobility. In particular, a group of West Point graduates such as Robert Lee, Zachary Taylor, Ulysses Grant and others showed high command skills. In particular, Scott used his knowledge to formulate a thorough combat plan and successfully commanded the landing of Veracruz and the siege of Mexico City. Wellington, a famous British soldier at the time, once praised him as "the greatest soldier alive." Said the Battle of Veracruz-Mexico City was "unparalleled in military history." The US-Mexico War had many firsts in U.S. military history: the first time the U.S. military fought in a foreign country, the first amphibious landing, the first street fighting, the first time the use of steam warships, the first time the establishment of a military government in an enemy country, and the first time the war was fought by a professional army alone. The territory expanded during the war was vast and rich in resources, laying the foundation for American industrialization. However, territorial expansion also promoted the development of slavery in the southern United States, intensified the conflict between the north and the south, and laid the seeds for future civil wars. Through this not-so-large-scale war, the United States seized 2.3 million square kilometers of land and became a major country across the Atlantic and Pacific Oceans, a rare sight in the world. Mexico has lost most of its territory and its vitality has been greatly damaged. The United States has since gained dominance in the Americas. Map of Mexico in 1847