“Manifest Destiny” and the US vs. Mexico War


The Mexican war commenced in 1845, under the expansionist-mindset administration of President James K. Polk. President Polk had the idea that the US had a “manifest destiny to spread across the continent to the Pacific Ocean.” In the period leading to the declaration of war by the US against Mexico, there were negotiations regarding the delicate issue of the US and Mexican border. This paper will focus on this conflict that arose between the US and Mexico and the war that ensued after an amicable solution was not agreed upon by both countries. This paper asks and seeks to elucidate the crucial questions regarding the Mexican war. What was the role of the “manifest destiny” in the conflict between the two sovereign nations? Was the Mexican war justified, and what are the supporting arguments for the declaration of war? This essay will offer in-depth analysis of the Mexican war and the mitigating circumstances surrounding the conflict.

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The Influence of “manifest destiny” in the Mexican- American Conflict

In the periods of the 1840’s, the American administration was keen on the idea of manifest destiny. The notion of “manifest destiny” was based on the belief and understanding that the US should broaden its borders from the Atlantic to the Pacific Ocean(Gast). However, this desire was faced by some obstacles since some of the regions in their plan were in foreign territories. The southwestern and western lands which included regions of Texas were occupied by the Mexicans while the Oregon region was occupied in partnership with the British. President Polk ran an aggressive campaign for the manifest destiny showing deep commitment in actualizing this goal(Gast). He further ran campaign slogans suggesting “54’40 of Fight.” The British settle with the Americans regarding the Oregon territory while the Mexicans proved difficult in their negotiations for the western and southwestern region. President Polk was adamant in his quest for the manifest destiny that he sent troops to occupy the disputed lands between the Rio Grande and Nueces. When the Mexican president refused to meet with Polk’s emissary, Slidell, Pres Polk considered this act of defiance and the subsequent killing of American troops as a sign for a declaration of war.

Arguments Raised Regarding the Mexican- American War

The conflict received widespread support by the Americans based on their need for manifest destiny. The people in favor of the conflict believed that US should dominate the continent and they should extend their boundaries across from the east to the west coast. Additionally, they maintained that it was the duty of America to stretch its “boundary of freedom” and spread its notions of idealism and democracy to other territories who were willing to accommodate a system of self-government(Clay). It is easy to conclude that “manifest destiny” was based on the need for economic, political and social pressures by the Americans to occupy the foreign territories.

There were dissenting voices that did not root for the Mexican-American war especially from the northerners. The Northern Whigs opposed this engagement by Pres Polk since they believed there was an absence of truthfulness and constitutionality in the president’s action(Clay). They maintained Pres Polk failed to sufficiently disclose the encroachment by American troops was the cause of the engagement by the Mexican military on the American soldiers. Some of the dissenting voices based their fears on the possible increase in slave states.

Justification of the Mexican- American Conflict

The war took place during the period where America was expanding, and the wheels of revolution could not be stopped. In my personal opinion, I believe America’s deeds in the conflict were justified. My belief is based on the opportunities America was willing to offer to the new territories that were in Mexico. In the spirit of “manifest destiny,” America was going to benefit politically and economically(Clay). Subsequently, the inhabitants of the territories would not be left behind, and they were going to benefit from the same. America possessed a stable economy and established institutions which had the capacity of proving for the existing population, and it was generous enough to accommodate the new entrances.


At the beginning of this paper, a few questions were raised regarding the Mexican-American war. For the essay to provide an understanding of the thesis statements highlighted in the onset, the piece has provided a distinct outlook of the conflict between US and Mexico in 1845. It is essential to note as expressed in the essay, the war took place from April 1846 to February 1848, when the “Treaty of Guadalupe” was signed. The paper has keenly stated and answered the key questions raised at the beginning of the writing. It has identified the key issues that were raised by the Northern Whigs who were against the move by President Polk in his quest for manifest destiny. The paper has vividly articulated the origin of “manifest destiny” which was an idea upheld by Pres Polk’s administration which was evident from the declaration of war against Mexico.


Work Cited

A-War-President-Progressive-Democracy-Presidential-Campaign-1848-E9BED7.Jpg (JPEG Image, 1300 × 1110 Pixels) – Scaled (35%). http://c8.alamy.com/comp/E9BED7/a-war-president-progressive-democracy-presidential-campaign-1848-E9BED7.jpg. Accessed 9 Nov. 2017.

Clay, Henry. Speech on the Mexican-American War. Accessed 9 Nov. 2017.

Gast, John. Picturing US History – John Gast, American Progress, 1872. Accessed 9 Nov. 2017.

HarpWeek | American Political Prints 1766-1876 | Medium Image. http://loc.harpweek.com/LCPoliticalCartoons/IndexDisplayCartoonMedium.asp?SourceIndex=People&IndexText=&UniqueID=2&Year=1846. Accessed 9 Nov. 2017.

Plucked or, The Mexican Eagle before the War! The Mexican Eagle after the War! 1847, //www.loc.gov/pictures/resource/cph.3a01957.

President Polk’s Address to Congress, May 11, 1846. Accessed 9 Nov. 2017.