The Manifest Destiny is the idea of continental expansion by the United States, from the Atlantic to the Pacific Oceans, which naturally occurred out of a deep want and need to explore and conquer new lands and establish new borders. This idea contributed to several wars, including the US-Mexican War.
Mexico and the United States had its share of territorial issues. With only four more days of his presidency, on March 1, 1845, President John Tyler signed the Texas annexation bill. When the United States formally offered annexation to Texas in 1845, Mexico, protested. On December 29, 1845, Texas was formally admitted to the Union. Mexico refused to accept the loss of Texas, as written in the Treaty of Velasco that was created after the Battle of San Jacinto, in April 21, 1836, and still considered Texas to be Mexican territory, which obtained independence from Spain in 1821, that was under temporary rule of a rebel government. Mexico declared that the annexation of Texas was the same as an act of war. Around the same time, American President, James K. Polk (who took office on March 4, 1845) sent diplomat John Slidell to Mexico with an offer to buy Texas, New Mexico and California for about $30 million. Mexico rejected the offer.
President Polk wanted to define the “borderline” of America. He sent orders to US Army General Zachary Taylor to set up a defense system on the north bank of the Rio Grande River. In addition, Polk also wanted to influence the people who lived in the region to pressure the Mexicans to sell off the territory that was not actually under any established form of government at that time since Mexico’s frontiers had no formal king or leader. Polk ordered US Colonel Stephen Kearney to the New Mexico territory, and He also ordered the US navy to block off Mexican ports in the Gulf of Mexico.
On April 25, 1846, Mexican troops crossed north of the Rio Grand River and the first shots were fired. President Polk received word that Mexican forces had ambushed two of General Taylor's companies along the Rio Grande. On May 11, 1846, President Polk asked Congress to declare war on Mexico, stating the following: "After reiterated menaces, Mexico has passed the boundary of the United States, has invaded our territory and shed American blood upon the American Soil. She has proclaimed that hostilities have commenced, and that the two nations are at war." (1) Two days later, the US Congress overwhelmingly votes in favor of President James K. Polk's request to declare war on Mexico.
American military forces took up several major campaigns in the course of the war resulting in significant battles that occurred throughout the region. American Brigadier General Stephen Kearney led a small force to seize Santa Fe and the New Mexico territory, and then marched west to California. There he met up with an American force and eventually secured the completion of the Bear Flag Revolt; American settlers declared their independence from Mexico....