Manifest Destiny/Mexican American War

The conflict is significant due to several reasons:
- It represents a struggle between two republics over disputed land claims.
- The war is characterized as being provoked by the United States, aiming to acquire territory it was not originally entitled to possess.
- The outcome risks reigniting the debate over the expansion of slavery, which was ostensibly settled in the 1820s by the Missouri Compromise.

Annexation of Texas (1844)
- The United States decides to admit the Republic of Texas as a state.
- Mexico refuses this annexation as it has never recognized Texas as an independent republic.
- The crux of the dispute centers on the delineation of the Texas-Mexico border:
- Possibility 1: Nueces River
- Possibility 2: Rio Grande
- The Treaty of Velasco set the Rio Grande as the border; however, Mexico contested this, asserting that the Nueces River was the legitimate boundary since the 1700s, distinguishing between Tejas and Tamualipas provinces.

There was ambiguity regarding the extent of Texas’s western border post-independence:
- Texas claimed lands extending south to the Rio Grande and west/north, covering parts of modern-day New Mexico, Oklahoma panhandle, Colorado, and even into Wyoming.
- These lands were integral to Mexico and extended far beyond original Tejas province borders.

Reasons for Texas's Admission:
- Polk believed Texas should be admitted as one state, affirming its status as a slave state.
- Aimed to acquire ALL Mexican territories north of the Rio Grande to fulfill the idea of Manifest Destiny—expanding the U.S. from the Atlantic to the Pacific coasts.
- Promoted the idea that the U.S. could achieve this fulfillment relatively soon (post-1845), just years after the inception as an independent nation post-Constitution ratification.

December 1845: Polk presents Mexico with an offer of $30 million for all territory north of the Rio Grande, demanding the recognition of the Rio Grande as the U.S.-Mexico border.
January 1846: Mexico rejects the offer, preparing to defend against U.S. aggression despite their military unpreparedness.
Significance of Territory Acquisition:
- Gaining access to Pacific ports and expanding U.S. territorial size significantly, risking capitulation of half of Mexican land claims in North America.

By 1846, Mexico was significantly weakened post-independence from Spain, facing multiple regime changes and an unstable government.
Military Challenges:
- Limited military resources, with many troops and volunteers refusing to fight, leading to a mobilized force of less than 10,000, while the U.S. had 20,000 troops.
- Historical context documented through historian Josefina Zoraida Vazquez who cited Mexico's financial instability, outdated weaponry, and political division leading to military disadvantage against the U.S.

February 1846: Polk’s orders for troops across the Nueces River into territory disputed with Mexico, serving as a provocation of conflict.
April 1846: A confrontation leads to the death of 11 American soldiers, which Polk uses to justify war declaring it a matter of “just cause”.
May 13, 1846: Congress approves the Declaration of War amid strong dissent from the Whig Party.

The war was characterized by extreme brutality, with little distinction made between armed forces and civilians:
- Major destruction of Mexican cities and territories through widespread violence, with casualties affecting both Mexican military and civilian populations.
- Political support fractured: Democrats generally in favor, while the Whig party vehemently opposed the conflict.
- Specific incidents such as artillery fire on civilian structures like the Convent of Churubusco, killing hundreds of civilians, illustrate the war's impact.
- Reflective thoughts by President Ulysses S. Grant, who acknowledged his opposition to the war, labeling it unjust, condemning the lack of moral standing in waging conflict against a weaker nation.

Manifest Destiny Accomplished:
- Successfully fulfilled rhetoric of U.S. expansionism with a relatively low casualty rate for the United States, contrasting sharply with significant losses incurred by Mexico.
- Cultural memory in Mexico framed war as “el dismembramiento”, instilling a sense of lasting resentment towards the U.S. and prompting memorials in Mexico for fallen soldiers.
- The war created a complex question of national identity for the U.S., challenging notions of fighting conquest wars, especially against a neighboring republic.

Revived Political Tension:
- New territories acquired from Mexico reignited contentious dialogues regarding the expansion of slavery, a topic previously settled by the Missouri Compromise.
- Resurfacing of national tensions centered around slavery positioning may lead to an impending crisis as abolitionist sentiments gained traction, raising concerns for future political stability and civil discourse in the United States.