Multiple choice What was one of James K. Polk's major beliefs about the United States? It was meant to conquer the entirety of Mexico. All Mexican lands were not to be touched by the US. The United States should never enter a war close to home. It had a manifest destiny to spread across to the Pacific. Reveal answer Fill a bubble to check yourself D Correct answer Explanation President James K. Polk was a strong proponent of Manifest Destiny, the 19th-century belief that the United States was divinely ordained to expand its territory across the North American continent to the Pacific Ocean.