May 8, 1846 · Northern Mexico Theater

The opening land battle of the Mexican-American War, fought on flat chaparral prairie near the Rio Grande. General Taylor's Army of Occupation met a larger Mexican force under Arista that had crossed the river. American artillery — particularly the 'flying artillery' batteries of Ringgold and Duncan — proved devastatingly effective against Mexican infantry formations, repeatedly breaking up charges before they could close.

May 9, 1846 · Northern Mexico Theater

Fought the day after Palo Alto in dense chaparral that negated Mexican numerical advantages and neutralized artillery. American forces pushed aggressively through the brush, captured Mexican artillery, and broke the enemy line. Captain Charles May's dragoon charge captured Mexican General Vega. The routed Mexican army fled toward and across the Rio Grande, suffering heavy losses in the crossing.

September 21–24, 1846 · Northern Mexico Theater

A fierce four-day urban battle for the heavily fortified city of Monterrey in northeastern Mexico. Taylor divided his force, sending Worth's division to cut the western road while he attacked from the east. American soldiers fought house-to-house through the city's narrow streets, using picks and crowbars to break through walls rather than expose themselves in the open. After heavy casualties on both sides, Ampudia negotiated an eight-week armistice and withdrew his army — a decision that angered President Polk.

February 22–23, 1847 · Northern Mexico Theater

Santa Anna marched an army of roughly 15,000 north from San Luis Potosí to destroy Taylor's reduced force of fewer than 5,000 men near the hacienda of Buena Vista. In two days of desperate fighting in a mountain pass, American artillery and the Mississippi Rifles regiment — led by Colonel Jefferson Davis — repeatedly broke Mexican charges. Santa Anna withdrew despite his numerical advantage, claiming victory but effectively ending offensive operations in the north.

March 9–29, 1847 · Central Mexico Theater

General Winfield Scott executed the largest amphibious operation in American history to that date, landing 12,000 troops on the beaches south of Veracruz and laying siege to the heavily fortified port city. Naval bombardment and army siege artillery systematically reduced the city's defenses. After three weeks, the garrison of Veracruz surrendered, giving Scott a vital base of operations and supply port for his advance toward Mexico City.

April 17–18, 1847 · Central Mexico Theater

Santa Anna positioned a large army in the mountain pass of Cerro Gordo along the National Highway, believing the position impregnable. Captain Robert E. Lee, conducting reconnaissance through seemingly impassable terrain, discovered a flanking route that allowed American forces to outflank the Mexican position entirely. The flanking column cut off the Mexican line of retreat and the position collapsed in a rout, nearly capturing Santa Anna himself.

August 19–20, 1847 · Valley of Mexico Theater

In the approach to Mexico City, American forces used the Pedregal — a massive lava field — to outflank Mexican defenses. Once again Lee conducted the key reconnaissance, finding a path through the Pedregal that allowed a flanking force under Persifer Smith to reach Valencia's rear. The assault lasted only seventeen minutes, routing Valencia's force and sending survivors fleeing toward Churubusco.

August 20, 1847 · Valley of Mexico Theater

Fought the same day as Contreras, Churubusco was the bloodiest single engagement of the war. Mexican forces made a determined stand at the fortified convent of San Mateo and a bridgehead over the Churubusco River. The Saint Patrick's Battalion — Irish-American deserters who had joined the Mexican side — fought with particular ferocity. After hours of close combat the positions were overwhelmed, but at a cost that shocked American commanders.

September 8, 1847 · Valley of Mexico Theater

Based on faulty intelligence that cannon were being cast at Molino del Rey near Chapultepec, Worth's division attacked the stone buildings. The assault encountered far stronger resistance than expected — the Mexican defenders were well-positioned and fought stubbornly. American forces ultimately carried the position but suffered casualty rates that appalled Scott and raised questions about the necessity of the attack.

September 13, 1847 · Valley of Mexico Theater

Chapultepec Castle, sitting atop a rocky hill and serving as Mexico's national military academy, was the last major fortification before Mexico City. Scott's assault combined artillery bombardment with simultaneous infantry scaling-ladder assaults from multiple directions. The cadets of the military college — the Niños Héroes — fought alongside regular troops and several died rather than surrender. The castle fell in bitter fighting, and two American officers — including young Lt. Ulysses S. Grant — took initiative to haul artillery pieces into church towers, accelerating the Mexican collapse.

September 13–14, 1847 · Valley of Mexico Theater

Following the fall of Chapultepec, American columns advanced along the causeways into Mexico City through the night of September 13–14. Street fighting continued through the early morning hours as Mexican soldiers and armed civilians resisted the advance. Santa Anna evacuated the city rather than allow it to become a charnel house. On the morning of September 14, 1847, General Scott rode into the Grand Plaza and the Stars and Stripes were raised over the National Palace — the Hall of Montezuma.