Why The U.s. Was not Justified in Going to War with Mexico

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About this sample

About this sample


Words: 866 |

Pages: 2|

5 min read

Published: Sep 12, 2023

Words: 866|Pages: 2|5 min read

Published: Sep 12, 2023

Table of contents

  1. Territorial Disputes: Questionable Claims to Mexican Land
  2. The Controversial Outbreak of War: Polk's Role
  3. Ethical Concerns: The Impact on Mexico and Indigenous Peoples
  4. Conclusion

The Mexican-American War, a two-year conflict between 1846 and 1848, has long been a subject of historical debate. While some argue that it was a necessary step for the United States to secure its interests and expand its territory, a critical examination reveals that the U.S. was not justified in going to war with Mexico. This essay will delve deeper into the key reasons behind this assertion, offering a more detailed analysis of territorial disputes, the controversial circumstances surrounding the war's outbreak, and the ethical concerns raised by the conflict.

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Territorial Disputes: Questionable Claims to Mexican Land

The heart of the territorial dispute lay in the ambiguous border between Texas and Mexico. The United States maintained that the border was the Rio Grande, a position based on the annexation of Texas in 1845. However, this annexation was contentious from the outset, as Mexico had never formally recognized Texan independence following its declaration in 1836. Mexico argued that the border was the Nueces River, which lay further north. This disagreement over the border's location was a central issue that led to the war.

From a legal and diplomatic perspective, the United States had not effectively established a clear and internationally recognized border with Mexico. This lack of clarity should have prompted a diplomatic resolution rather than a resort to military force. Instead, the U.S. government, under President James K. Polk, decided to send General Zachary Taylor and troops across the Rio Grande into territory disputed by Mexico. This aggressive action not only escalated tensions but also challenged the U.S.'s claim to a justifiable cause for war.

Furthermore, the concept of Manifest Destiny, which was prevalent at the time, fueled the belief among Americans that the nation was destined to expand across the continent. This ideology played a significant role in justifying the war, as it framed the conflict as a means to fulfill America's destiny. However, Manifest Destiny should not serve as a legitimate basis for territorial expansion at the expense of another sovereign nation, especially when legal and diplomatic avenues remained unexplored.

The Controversial Outbreak of War: Polk's Role

Examining the circumstances surrounding the outbreak of the Mexican-American War reveals significant controversies, particularly concerning President Polk's actions. Polk, an advocate for westward expansion, is suspected of intentionally provoking Mexico into military conflict to further territorial acquisition. His administration dispatched Taylor and troops to the disputed Texas-Mexico border region, fully anticipating that this move would lead to hostilities.

Congressman Abraham Lincoln, through the "spot resolutions," sought to challenge Polk's justification for the war. Lincoln argued that the president had failed to provide evidence of the exact location of the alleged Mexican aggression, highlighting the war as a choice rather than a necessity. This further underscores the war's questionable justification and raises concerns about its true motives.

Moreover, Polk's aggressive posture towards Mexico can be seen as part of a larger pattern of American expansionism. The U.S. had previously acquired vast territories through negotiations and, at times, force. The Mexican-American War was another instance where territorial ambitions took precedence over diplomacy and peaceful dispute resolution.

Ethical Concerns: The Impact on Mexico and Indigenous Peoples

Beyond the legal and diplomatic issues, the Mexican-American War raised profound ethical concerns. The war resulted in the loss of thousands of lives on both sides, but it was Mexico that bore the brunt of the suffering. Mexican civilians, soldiers, and indigenous populations endured the horrors of war, including violence, displacement, and economic devastation.

The Treaty of Guadalupe Hidalgo, which ended the war in 1848, imposed harsh terms on Mexico. The U.S. acquired significant territories, including present-day California, Arizona, New Mexico, Texas, and more, in exchange for a modest financial settlement. This outcome disproportionately favored the United States and further weakened Mexico, a nation already grappling with internal strife and economic difficulties. The U.S. expansionism at Mexico's expense, driven by territorial ambitions, raises moral questions about the justifiability of the war.

Additionally, the war had a devastating impact on indigenous peoples living in the newly acquired territories. Their ancestral lands were often seized, and they faced violence and displacement. The U.S. government's failure to protect the rights and well-being of these indigenous populations in the aftermath of the war underscores the ethical concerns associated with the conflict.

The long-term consequences of the Mexican-American War extended beyond the immediate territorial gains. It left a legacy of distrust and tension between the United States and Mexico, which endured for generations. The scars of the war and its ethical implications cannot be easily dismissed, making it a pivotal event in American history that warrants ongoing examination and reflection.


In conclusion, a comprehensive analysis reveals that the U.S. was not justified in going to war with Mexico during the Mexican-American War. The territorial disputes were marked by ambiguity and lacked a clear legal basis, undermining the U.S. claim to military necessity. The controversial circumstances surrounding the outbreak of the war, particularly President Polk's actions, raise doubts about its true motives.

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Moreover, the ethical concerns associated with the impact on Mexico and indigenous populations highlight the disproportionate suffering caused by the conflict. The Mexican-American War remains a contentious chapter in American history, serving as a reminder of the complexities involved in justifying military actions and the importance of diplomacy and ethical considerations in international relations.

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Dr. Charlotte Jacobson

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Why the U.S. Was Not Justified in Going to War with Mexico. (2023, September 12). GradesFixer. Retrieved June 23, 2024, from
“Why the U.S. Was Not Justified in Going to War with Mexico.” GradesFixer, 12 Sept. 2023,
Why the U.S. Was Not Justified in Going to War with Mexico. [online]. Available at: <> [Accessed 23 Jun. 2024].
Why the U.S. Was Not Justified in Going to War with Mexico [Internet]. GradesFixer. 2023 Sept 12 [cited 2024 Jun 23]. Available from:
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