The United States in 1846 was not justified in going to war with Mexico. The United States did not have proper justification to respond with violence against the Mexican government. The war with Mexico was also a product of the United States' belief of manifest destiny. Polk's over ambition to seize new territory from the Mexicans and disappointment over their refusal to sell him California also possibly played a factor in his willingness to wage war against Mexico. The United States under the leadership of president Polk clearly provoked Mexico into attacking US troops. All these reasons show that the US had no business starting a war with Mexico for territory that was rightfully theirs.
The war with Mexico came at a time when much of the country had strong feelings of manifest destiny. Manifest destiny is the belief that fate had preordained the US to expand from the Atlantic to the Pacific oceans and from Canada to the Rio Grande river. This idea which was coined by John O' Sullivan was very popular in the 1840's. This ideal had strong influence and was one reason that their was so much popular support for the US expansion west. This ideal while nationalistic did not give us the right to go into Mexico and seize l
He told them on May 9, 1846 that he was to propose to congress that he wanted them to declare war on Mexico on the grounds that one: unpaid claims and two: Slidell's rejection. Quite possibly the strongest of all reasons that the US was unjust in going to war with Mexico in 1846 was that the US forces were in the disputed territory too purposely insight the Mexicans into starting the conflict so the US would look like they were the good guys in the incident. It had a president that was obsessed with fulfilling campaign promises and greed for new land. Yet the public was misled by this sense of manifest destiny and those that did support it supported an unjust war. Also the US provoked this boarder dispute into the two-year war that it became by purposely inciting the Mexicans into a fight. All these reasons are the evidence that the US was not justified in declaring war on Mexico. The US vision of manifest destiny helped to win the public's support for the Mexican war. This was a move to get the Mexicans to attack US troops on land that was claimed by both countries. They had the right to expel any US citizens that were living on their country's land especially if they where not abiding by their laws. Polk was so greedy for land that he was willing to risk blood shed and death of his citizens for revenge against the rejection of a proposed treaty and his want for manifest destiny. and which was rightfully theirs in the first place. This led Polk to frustration and his willingness to try backhanded and sneaky new ways to get the Mexicans to give him the territories that he desired. This alone makes even the annexation of Texas not completely just.