The decision by President James K. Polk that led to the Mexican-American War was his decision to annex Texas into the United States. In 1845, Texas was an independent republic after gaining independence from Mexico in 1836. Polk, who campaigned on a platform of territorial expansion, supported the annexation of Texas, seeing it as an opportunity to fulfill his Manifest Destiny agenda of expanding American territory from coast to coast. The Mexican government saw the annexation as a violation of their sovereignty and as a result, severed diplomatic relations with the United States. The unresolved border disputes and tensions between the two countries eventually led to the outbreak of the Mexican-American War in 1846.
