CAUSE
According to the Britannica website,
the Republic of Texas had won de facto independence from Mexico in the
Texas Revolution, which took place from 1835 to 1836. This included the
battle of the Alamo, which took place from February 23 to March 6, 1836.
The U.S. annexed the Republic of
Texas in 1845. U.S. diplomatic efforts to establish agreement on the
Texas-Mexico border and to purchase Mexico's California and New Mexico
territories failed. Mexico claimed that Texas ended at the Nueces
River; the U. S. Claimed that it ended at the Rio Grande. The war
resulted in the United States’ acquisition of more than 500,000 square
miles of Mexican territory extending westward from the Rio Grande to
the Pacific Ocean.
Mexico severed relations with the
United States in March 1845, shortly after the U.S. annexation of
Texas. In September, expansionist U.S. President James K. Polk sent
John Slidell on a secret mission to Mexico City to negotiate the
disputed Texas border, settle U.S. claims against Mexico, and purchase
New Mexico and California for up to $30 million. Mexican President José
Joaquín Herrera, aware in advance of Slidell’s intention of
dismembering the country, refused to receive him. When Polk learned of
the snub, he ordered troops under General Zachary Taylor to occupy the
disputed area between the Nueces and the Rio Grande; this took place in
January 1846.
WAR
On May 9, 1846, Polk began to
prepare a war message to Congress, justifying hostilities on the
grounds of Mexican refusal to pay U.S. claims and refusal to negotiate
with Slidell. That evening he received word that Mexican troops had
crossed the Rio Grande on April 25 and attacked Taylor’s troops,
killing or injuring 16 of them. In his quickly revised war message -
delivered to Congress on May 11 - Polk claimed that Mexico had “invaded
our territory and shed American blood on American soil.” Congress
overwhelmingly approved a declaration of war on May 1.
When war broke out, former Mexican
president and general Antonio López de Santa Anna (the vanquisher of
the Texan forces at the Alamo in 1836) contacted Polk. The U.S.
president arranged for a ship to take Santa Anna from his exile in Cuba
to Mexico for the purpose of working for peace. Instead of acting for
peace, however, on his return, Santa Anna took charge of the Mexican
forces.
Following its original plan for the
war, the United States sent its army from the Rio Grande, under Taylor,
to invade the heart of Mexico while a second force, under Colonel
Stephen Kearny, was to occupy New Mexico and California. Kearny’s
campaign into New Mexico and California encountered little resistance,
and the residents of both provinces appeared to accept U.S. occupation
with a minimum of resentment. Meanwhile, Taylor’s army fought several
battles south of the Rio Grande, captured the important city of
Monterrey, and defeated a major Mexican force at the Battle of Buena
Vista in February 1847. But Taylor showed no enthusiasm for a major
invasion of Mexico, and on several occasions he failed to pursue the
Mexicans vigorously after defeating them. In disgust, Polk revised his
war strategy. He ordered General Winfield Scott to take an army by sea
to Veracruz, capture that key seaport, and march inland to Mexico City.
Scott took Veracruz in March after a siege of three weeks and began the
march to Mexico City. Despite some Mexican resistance, Scott’s campaign
was marked by an unbroken series of victories, and he entered Mexico
City on September 14, 1847. The fall of the Mexican capital ended the
military phase of the conflict.
RESOLUTION
Polk had assigned Nicholas Trist,
chief clerk in the State Department, to accompany Scott’s forces and to
negotiate a peace treaty. But after a long delay in the formation of a
new Mexican government capable of negotiations, Polk grew impatient and
recalled Trist. Trist, however, disobeyed his instructions and on
February 2, 1848, signed the Treaty of Guadalupe Hidalgo. According to
the treaty, which was subsequently ratified by both national
congresses, Mexico ceded to the United States nearly all the territory
now included in the states of New Mexico, Utah, Nevada, Arizona,
California, Texas, and western Colorado for $15 million and U.S.
assumption of its citizens’ claims against Mexico.
