Mexican-American War: Battle of Monterrey

Fighting near Monterrey, 1846
Battle of Monterrey. Photograph Source: Public Domain

The Battle of Monterrey was fought September 21-24, 1846, during the Mexican-American War (1846-1848) and was the first major campaign of the conflict conducted on Mexican soil. Following the initial fighting in southern Texas, American troops led by Major General Zachary Taylor crossed the Rio Grande and pushed into northern Mexico with the goal of taking Monterrey. Nearing the city, Taylor was forced to launch assaults against its defenses as he lacked the artillery to conduct a siege. The resulting battle saw American troops capture the city after taking heavy casualties as they fought through Monterrey's streets.

American Preparations

Following the Battles of Palo Alto and Resaca de la Palma, American forces under Brigadier General Zachary Taylor relieved the siege of Fort Texas and crossed the Rio Grande into Mexico to capture Matamoros. In the wake of these engagements, the United States formally declared war on Mexico and efforts began to expand the U.S. Army to meet wartime needs. In Washington, President James K. Polk and Major General Winfield Scott commenced devising a strategy for winning the war.

While Taylor received orders to push south into Mexico to capture Monterrey, Brigadier General John E. Wool was to march from San Antonio, TX to Chihuahua. In addition to capturing territory, Wool would be in a position to support Taylor's advance. A third column, led by Colonel Stephen W. Kearny, would depart Fort Leavenworth, KS and move southwest to secure Santa Fe before proceeding on to San Diego.

To fill the ranks of these forces, Polk requested that Congress authorize the raising of 50,000 volunteers with recruitment quotas assigned to each state. The first of these ill-disciplined and rowdy troops reached Taylor's camp shortly after the occupation of Matamoros. Additional units arrived through the summer and badly taxed Taylor's logistical system. Lacking in training and overseen by officers of their choosing, the volunteers clashed with the regulars and Taylor struggled to keep the newly-arrived men in line.

General Winfield Scott. Photograph Source: Public Domain

Assessing the avenues of advance, Taylor, now a major general, elected to move his force of around 15,000 men up the Rio Grande to Camargo and then march 125 miles overland to Monterrey. The shift to Camargo proved difficult as the Americans battled extreme temperatures, insects, and river flooding. Though well-positioned for the campaign, Camargo lacked sufficient fresh water and it proved difficult to maintain sanitary conditions and prevent disease.

The Mexicans Regroup

As Taylor prepared to advance south, changes occurred in the Mexican command structure. Twice defeated in battle, General Mariano Arista was relieved from command of the Mexican Army of the North and ordered to face a court-martial. Departing, he was replaced by Lieutenant General Pedro de Ampudia.

A native of Havana, Cuba, Ampudia had started his career with the Spanish but defected to the Mexican Army during the Mexican War of Independence. Known for his cruelty and cunning in the field, he was ordered to establish a defensive line near Saltillo. Ignoring this directive, Ampudia instead elected to make a stand at Monterrey as defeats and numerous retreats had badly damaged the morale of the army.

Battle of Monterrey

  • Conflict: Mexican-American War (1846-1848)
  • Dates: September 21-24, 1846
  • Armies and Commanders:
  • Americans
  • Major General Zachary Taylor
  • 6,220 men
  • Mexico
  • Lieutenant General Pedro de Ampudia
  • approx. 10,000 men
  • Casualties:
  • Americans: 120 killed, 368 wounded, 43 missing
  • Mexicans: 367 killed and wounded

Approaching the City

Consolidating his army at Camargo, Taylor found that he only possessed wagons and pack animals to support around 6,600 men. As a result, the remainder of the army, many of whom were ill, was dispersed to garrisons along the Rio Grande while Taylor began his march south. Departing Camargo on August 19, the American vanguard was led by Brigadier General William J. Worth. Marching towards Cerralvo, Worth's command was forced to widen and improve the roads for the men following. Moving slowly, the army reached the town on August 25 and after a pause pressed on to Monterrey.

A Strongly Defended City

Arriving just north of the city on September 19, Taylor moved the army into camp in an area dubbed Walnut Springs. A city of around 10,000 people, Monterrey was protected to the south by the Rio Santa Catarina and the mountains of the Sierra Madre. A lone road ran south along the river to Saltillo which served as the Mexicans' primary line of supply and retreat.

To defend the city, Ampudia possessed an impressive array of fortifications, the largest of which, the Citadel, was north of Monterrey and formed from an unfinished cathedral. The northeast approach to the city was covered by an earthwork dubbed La Teneria while the eastern entrance was protected by Fort Diablo. On the opposite side of Monterrey, the western approach was defended by Fort Libertad atop Independence Hill.

Across the river and to the south, a redoubt and Fort Soldado sat atop Federation Hill and protected the road to Saltillo. Utilizing intelligence gathered by his chief engineer, Major Joseph K. F. Mansfield, Taylor found that while the defenses were strong, they were not mutually supporting and that Ampudia's reserves would have difficulty covering the gaps between them.


With this in mind, he determined that many of the strong points could be isolated and taken. While military convention called for siege tactics, Taylor had been forced to leave his heavy artillery at the Rio Grande. As a result, he planned a double envelopment of the city with his men striking at the eastern and western approaches.

To carry this out, he re-organized the army into four divisions under Worth, Brigadier General David Twiggs, Major General William Butler, and Major General J. Pinckney Henderson. Short on artillery, he assigned the bulk to Worth while assigning the remainder to Twiggs. The army's only indirect fire weapons, a mortar and two howitzers, remained under Taylor's personal control.

Major General William Worth in blue U.S. Army uniform.
Major General William J. Worth. National Archives and Records Administration

For the battle, Worth was instructed to take his division, with Henderson's mounted Texas Division in support, on a wide flanking maneuver to the west and south with the goal of severing the Saltillo road and attacking the city from the west. To support this movement, Taylor planned a diversionary strike on the city's eastern defenses. Worth's men began moving out around 2:00 PM on September 20. Fighting began the next morning around 6:00 AM when Worth's column was attacked by Mexican cavalry.

These assaults were beaten off, though his men came under increasingly heavy fire from Independence and Federation Hills. Resolving that these would need to be taken before the march could continue, he directed troops to cross the river and attack the more lightly defended Federation Hill. Storming the hill, the Americans succeeded in taking the crest and capturing Fort Soldado. Hearing firing, Taylor advanced Twiggs' and Butler's divisions against the northeastern defenses. Finding that Ampudia would not come out and fight, he began an attack on this part of the city (Map).

A Costly Victory

As Twiggs was ill, Lieutenant Colonel John Garland led elements of his division forward. Crossing an open expanse under fire, they entered the city but began taking heavy casualties in street fighting. To the east, Butler was wounded though his men succeeded in taking La Teneria in heavy fighting. By nightfall, Taylor had secured footholds on both sides of the city. The next day, the fighting focused on the western side of Monterrey as Worth conducted a successful assault on Independence Hill which saw his men take Fort Libertad and an abandoned bishop's palace known as the Obispado.

American troops fighting in the street of Monterrey
U.S. Army troops attack through the streets of Monterrey, 1846. Public Domain 

Around midnight, Ampudia ordered the remaining outer works, with the exception of the Citadel, to be abandoned (Map). The next morning, American forces began attacking on both fronts. Having learned from the casualties sustained two days earlier, they avoided fighting in the streets and instead advanced by knocking holes through the walls of adjoining buildings.

Though a tedious process, they steadily pushed the Mexican defenders back towards the city's main square. Arriving within two blocks, Taylor ordered his men to halt and fall back slightly as he was concerned about civilian casualties in the area. Sending his lone mortar to Worth, he directed that one shell be fired at the square every twenty minutes. As this slow shelling began, the local governor requested permission for noncombatants to leave the city. Effectively surrounded, Ampudia asked for surrender terms around midnight.


In the fighting for Monterrey, Taylor lost 120 killed, 368 wounded, and 43 missing. Mexican losses totaled around 367 killed and wounded. Entering surrender negotiations, the two sides agreed to terms that called for Ampudia to surrender the city in exchange for an eight-week armistice and allowing his troops to go free. Taylor consented to the terms largely because he was deep in enemy territory with a small army that had just taken significant losses.

Learning of Taylor's actions, President James K. Polk was irate stating that army’s job was to “kill the enemy” and not to make deals. In the wake of Monterrey, much of Taylor’s army was stripped away to be used in an invasion of central Mexico. Left with the remnants of his command, he won a stunning victory at the Battle of Buena Vista on February 23, 1847.


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Your Citation
Hickman, Kennedy. "Mexican-American War: Battle of Monterrey." ThoughtCo, Sep. 9, 2021, Hickman, Kennedy. (2021, September 9). Mexican-American War: Battle of Monterrey. Retrieved from Hickman, Kennedy. "Mexican-American War: Battle of Monterrey." ThoughtCo. (accessed May 29, 2023).