Mexican War.

The Mexican-American War was based on the Americans trying to expand their territory. They thought that some parts of Mexico was a good idea so they tried to buy the lands from Mexico, using an excuse that they want payback from the Mexico's owe to America during the Spanish War. The Mexicans refused, and when they surprisingly attacked a small American station, President James K. Polk of the United States wrote a letter to the …

…Meanwhile, Polk ordered General Zachary Taylor with 4,000 men to station on the Nueces River and advance to Rio Grande. On April 25th, the Mexicans surprisingly attacked and defeated them. After the assault, Polk asks the Congress to declare war on Mexico, saying that Mexico invaded USA's territory. In reality, Mexico has a good claim as the battle took place on just north of Rio Grande. However, on May 13th, 1846, the Congress declares war on Mexico.