AP US History in 1 Minute Daily: Causes of War with Mexico (Day 122/309)

Welcome to today’s explanation of the Causes of War with Mexico in my series- APUSH in 1 Minute Daily!

Texas-Tyler Treaty, Texas State Library

When Texas declared independence, Mexico warned the U.S. that American annexation of the region would mean war. After Polk’s victory and subsequent Texan statehood, a Mexican ambassador declared it as “an act of war.”

Border Disputes with Texas and Mexico, Britannica

Since Texan independence, official Texan and Mexican boundaries had been disputed. While Mexico viewed the Nueces River as the boundary, Texas established the far more southern Rio Grande as the border.

John Slidell, Wikimedia Commons

President Polk sent a special envoy, John Slidell, to Mexico to settle the disputed border and to persuade Mexico to sell California and the New Mexico territories. However, Slidell failed to achieve his mission.

Mexican-American War, Wikimedia Commons

Polk ordered General Zachary Taylor to approach the Rio Grande. Then, the Mexican military crossed the river and 11 Americans were killed in the ensuing battle. At Polk’s request, Congress officially declared war on Mexico.

The Mexican-American War began in 1846 due to failed diplomatic negotiations and border disputes. However, it was Polk’s order to send the American military into the contested territory that directly ignited the violent conflict.

Join me tomorrow as I explain the Effects of War with Mexico in the next APUSH in 1 Minute Daily!