Here you go, btw you should give more than 8 points ;/
Mexican War (1846–48).After weeks of fruitless diplomacy, the United States and the republic of Mexico declared war on each other in the spring of 1846. By the 1840s, many Americans held the view that the United States should reach from the Atlantic all the way to the Pacific Ocean. In 1844, Democrat James K. Polk of Tennessee ran for the presidency and won on a platform of expansionism, embracing the popular concept of “manifest destiny”—that God approved U.S. expansion throughout the continent. Polk opened diplomacy designed to redeem his campaign pledges to purchase California and other Mexican lands as well as to obtain the Oregon country from Britain. Considered in grand strategic terms, Polk intended to make the United States the undisputed national power on the North American continent and to obtain West Coast ports. The British agreed to an equitable treaty dividing Oregon, but no self‐respecting patriotic Mexican leader would be satisfied with any amount of money for California.
U.S. annexation of Texas sparked the war. The Texas Revolution of 1836 had won independence for the republic of Texas, but Mexico never officially recognized the loss of the province. Polk's predecessor, John Tyler, arranged the annexation of Texas into the United States in 1845 by a joint resolution of both Houses of Congress before Polk was sworn in. According to Mexico, the United States had torn away one of its provinces. The Mexican government rejected Polk's final offer of $35 million for California and other lands and dispatched military forces to the Rio Grande. It also rejected Texas and U.S. claims that the border extended south to the Rio Grande instead of the Nueces River.
On 23 April 1846, President Mariano Paredes announced that a state of “defensive” war existed between Mexico and the United States, in response to the violation of the Texas border by U.S. soldiers under Gen. Zachary Taylor, who marched under Polk's orders from Louisiana through Texas up to the Nueces River. On 25 April, Mexican and U.S. forces fought a skirmish between the Nueces and the Rio Grande. Eleven U.S. dragons were killed, five wounded and forty‐seven captured. It took several days for word of the skirmish to reach President Polk, who had previously decided on war even before Paredes's announcement. On 11 May, he asked Congress to acknowledge the state of war that Mexico had already announced, but did so with a resounding and controversial call: “American blood has been shed on American soil.” On 13 May, Congress strongly endorsed Polk's request, 174–14 in the House of Representatives and 40–2 in the Senate. Critics, mostly northern Whigs, condemned the president's action, asserting that he sought war to acquire more slave territory and denying that the disputed border area belonged to the United States.
Northern Mexico included two commercial centers, Santa Fe, New Mexico, and San Francisco, California. Lightly populated and distant from Mexico City, both provinces were difficult to defend. Polk met with his cabinet and formulated a remarkably ambitious strategy. He ordered U.S. soldiers to invade New Mexico, capture Santa Fe, then proceed to conquer California, where a naval squadron would assist them in securing the province. Meanwhile, General Taylor with less than 3,000 regulars would drive Mexican forces south of the Rio Grande, which the United States claimed as the international boundary. Polk assumed that if U.S. forces occupied the Rio Grande as well as key spots in New Mexico and California, Mexico would have no choice but to concede the fait accompli, and the United States would have won the war.
For their part, however, the Mexicans stood ready to fight, both for the defense of their territory and the future of their fledgling nation, which only twenty‐four years earlier had won its independence from Spain. Mexico possessed a tiny naval coast guard and on paper had a national army of more than 30,000 soldiers, over three times the U.S. Army's size at 8,500 officers and men. Numbers masked contrasts between the two armies, however. The Mexican Army was indifferently trained and unevenly equipped. Some units had enthusiastic officers, good weapons, and adequate supplies; others were deficient in all respects. Many Mexican officers held honorific commissions but knew little about military matters. The army had been involved with intrigues in the national capital, where commanders went in and out of favor with the political winds. Thus, the Mexican Army had more weaknesses than strengths.