The United States went to war in 1846 with Mexico. The war was the first major conflict based upon Manifest Destiny. Manifest Destiny is the belief that America had a God-given destiny to expand the country's borders from sea to shining sea. The war had two major causes.

The first major cause was the desire to expand the United States would cause conflict with the British in Canada, to the Mexicans in the southwest, and the Native Americans. Ever since President Jefferson acquired the Louisiana Territory in 1803, more and more Americans migrated westward.President Polk became President in 1845, the idea of expanding the United States' borders came into favor among him and the American people. In both 1835 and 1845, the United States offered to purchase California from Mexico for five million dollars and twenty-five million dollars. The Mexican government turned down the United States' offer.

Tension grew between Mexico and the United States when Texas became a United States' state. The second major cause of the war was the Texan War of Independence and the area to the United States. Not all American migration was unwelcome. In the 1820's and 1830's, Mexico needed people in he Northern parts of the country. An invitation was issued for people who would take an oath of allegiance to Mexico and convert to Catholicism.

Thousands of Americans liked this offer and moved, often with slaves, to the Mexican Province of Texas. Many of the people soon became mad with the way the government in Mexico city tried to run the province. In 1835, Texans fought and after many bloody battles, the Mexican President Santa Anna signed the Treaty of Velasco in 1836. Texas gained its independence but Mexicans refused to accept the document.

This triggered many border fights against Texas and Mexico.The Americans became unhappy with the Mexicans because of the conflicts. Texas joined the United States on July 4, 1845 because of the continued conflicts. Mexico did not like this and the undefined borders now became a major issue.

Texas, the United States, claimed the border at the Rio Grande River. Mexico claimed the land far north as the Nucees River. Both nations sent troops to enforce the borders. On April 25, 1846, a fight occurred between Mexican and American troops. The war had begun. The war of 1846 could not have been avoided.

A treaty would have only lasted for a while. The Treaty of Velasco caused a lot of conflicts.Another treaty with Mexico would do the same. The war helped settle the clash between Mexico and the United States. If the war never happened, Mexico and the United States would still have many different conflicts resulting in a war.

History would change dramatically. The countries would be different today in time. Mexico and the United States went to war in 1846. The war had two major conflicts. The Manifest Destiny was one conflict and the tension between the United States and Mexico when Texas became a United States' state was another conflict.

The war couldn't have been avoided. Many Americans and Mexicans died over this war.