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Why did President Polk send Zachary Taylor’s troops into the disputed territory between the Nueces River and the Rio Grande?

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How the Mexican-American War changed the U.S. forever — Mexican-American War Learn how the Mexican-American War ultimately pushed the United States closer to civil war.

President James K. Polk ordered General Zachary Taylor to occupy the disputed territory between the Nueces River and the Rio Grande primarily as a strategic maneuver to assert the U.S. claim to the borderland following failed diplomatic efforts.12

After the U.S. annexed Texas in 1845, Mexico severed diplomatic relations. Polk subsequently sent John Slidell on a secret mission to Mexico City to settle the border dispute and purchase New Mexico and California. When the Mexican government refused to receive Slidell, Polk ordered Taylor’s troops into the disputed area in January 1846.12

Polk simultaneously pursued diplomatic negotiations to acquire the territory, but the military occupation served to pressure Mexico and establish a physical presence in the region. When a skirmish occurred in the area in April 1846, Polk used the event to secure congressional support for a declaration of war, claiming that Mexico had invaded U.S. territory and shed American blood.21