In 1845, newly elected U.S. President James K. Polk, aware of the lingering instability in Mexico and eager to expand the United States to the Pacific Ocean, propositioned Mexico to purchase Alta California and Santa Fe de Nuevo México. The offer was flatly rejected by the Mexican government. Polk responded by moving U.S. troops, led by Zachary Taylor, into the Nueces Strip to provoke the Mexican Army into attacking the U.S. in order to get Congress to declare war. Taylor set up camp in a disputed border territory and refused to leave, even after repeated warnings from the Mexican government. After several skirmishes in the disputed zone, the U.S. Congress declared war on May 13, 1846.