In 1846, following its annexation of Texas, the United States went to war with Mexico over disputed territory in the Southwest and to enforce its declared southern boundary with Mexico: the Rio Grande. The U.S. president, James K. Polk, had campaigned on a policy platform of territorial expansion and sought to establish the United States as a hemispheric power. Polk coveted California and its natural, deepwater harbors — especially San Francisco.

A command initially assembled to enforce the U.S. southern boundary with Mexico, containing almost the entire professional U.S. Army and led by Maj. Gen. Zachary Taylor, marched south from the Rio Grande to the hills of the Sierra Madre Oriental. Taylor was a seasoned veteran of the War of 1812 and the Second Seminole War, but had never led an army on campaign. He had no experience in war as a senior commander to inform his judgments. The strategic guidance he received dwarfed his available means. His army had remarkable education, experience, and expertise: Four-fifths of its junior officers were trained at the U.S. Military Academy or fought against Seminole Indians in Florida. First ordered to the Rio Grande to defend newly annexed Texas, Taylor’s army transitioned in August to an offensive campaign to defeat Mexico and thereby ensure the final conquest of present-day Arizona, California, Nevada, Utah, Colorado, New Mexico, and Wyoming — all northern Mexico — which other U.S. forces had seized. Despite many difficulties, Taylor’s army succeeded.

The September 1846 Battle of Monterrey, long a hallmark of Zachary Taylor’s northern campaign, was a U.S. victory of strategy, operations, and tactics. Remembered in the historical literature as a deadly foray into urban combat and for its tactical blunders, the battle holds larger implications for the conduct of successful campaigns in war and sound strategy formulation. The inability of Taylor’s campaign to achieve decisive results in a limited, positional war, and the adaptation of American planning that resulted in the 1847 campaign for Mexico City, endure as illuminating examples of how military professionals can employ violent force to make enemies succumb to their will.