but specifically in Texas, New Mexico, northern and central California, and Eastern Mexico. This war began on the day that both troops met at the Rio Grande, and the Mexican army opened fire when Mexico claimed the Nueces River as its northeastern border whereas the U.S. claimed the Rio Grande River. The used-to-be established boundaries of the United States and Mexico changed when Mexico ceded immense territory of nearly one million square miles, including land in what is now California, Nevada, Utah, New Mexico, Arizona, Colorado, Wyoming, Oklahoma, and Kansas to the U.S.. This was significant because with this huge land acquisition, the issue of slavery in the new territories was raised. However, the United States was not justified going into war against Mexico due to robbery, expansion of slavery, and invasion provoked by the U.S.. The first reason why the U.S. was not justified for going to war with Mexico was the robbery of the Americans stealing Texas from Mexico. In Document C, Jesus Velasco-Marquez presented a Mexican viewpoint on the war with the United States stating, “As a consequence, the Mexican government reaffirmed the instruction to protect the border . . ." (Doc C). The second reason why U.S was not justified going to war with Mexico was the expansion of slavery. In Document D, “Objections to the Mexican-American War", Charles Sumner states, “Mexico, on achieving her independence of the Spanish Crown... decreed the abolition of human slavery within her dominions, embracing the province of Texas. . ." (Doc D). Americans moved into Texas while it still was Mexico’s land, they were against slavery, but Americans moved into Texas with their slaves regardless of Mexico's beliefs. The Americans just cared more for money and land rather than a slave, thus making Americans want to expand slavery.
The final reason why the U.S. was not justified going to war with Mexico was because the invasion of the United States provoked the war. In Document C, Jesus Velasco-Marquez presented a Mexican viewpoint on the war with the United States stating, ¨In the eyes of the (Mexican) government, the mobilization of the US army was an outright attack on Mexico . . .“ (Doc C). The U.S.was threatening the boundaries of Mexico’s land and as a reaction, Mexico defended themselves for their national security. Hence, why the U.S. was not justified going to war with Mexico due to the U.S. threatening their land thus provoking the war.