Battle of Monterrey In the Battle of Monterrey ( September 21 – 24 , 1846 ) during the Mexican - American War , General Pedro de Ampudia and the Mexican Army of the North was defeated by the Army of Occupation , a force of United States Regulars , Volunteers and Texas Rangers under the command of General Zachary Taylor . Background . After several defeats and near misses , the Mexican Army of the North , about 2 , 638 men ( 1st , 4th and 10th Line , two companies of the 6th and 2d Light Regiments , Mexico and Morelia Activos , 7th , 8th and Light Cavalry Regiments , and 13 pieces of artillery ) attempted to retreat south and refit before engaging United States forces under General Zachary Taylor . Near the old fortress town of Monterrey , General Pedro de Ampudia received orders from Antonio López de Santa Anna to retreat further to the city of Saltillo , where Ampudia was to establish a defensive line . But Ampudia , who was hungry for victory and conscious that his men were nearing mutiny through constantly being forced to retreat , refused the order and chose instead to make a stand at Monterrey . Joining Ampudia at this engagement were reinforcements from Mexico City totaling 3 , 140 men : 1 , 080 men of the Garcia - Conde Brigade ( Gen . Jose Garcia Conde ) ( Aguascalientes and Querétaro Battalions , two squadrons 3d Line Cavalry , three guns ( 3 - 8 lb ) ) , a thousand men of the Azpeitia Brigade ( Col . Florencio Azpeitia ) ( 3d Line , two squadrons Jalisco lancers , two squadrons Guanajuato Cavalry Regiment , six guns ( 8 & 12 lbs . ) and an Ambulance ) , 1 , 060 men of the Simeon Ramirez Brigade ( Acting Gen Ramirez ) ( 3d and 4th Light , three guns ( 1 - 8 lbs , 2 - 12 lbs ) & 3 howitzers 7 " ( Capt P . Gutierrez & Comdte A . Nieto ) ) and an artillery unit , the largely Irish - American volunteers for Mexico called " San Patricios " ( or the Saint Patrick ' s Battalion ) , in their first major engagement against U . S . forces . Battle . The Mexican strong points were at the Black Fort , the Tannery ( la Teneria ) , El Rincon del Diablo , Purisima tetes - de - pont ( two bridges ) , Ft . Libertad , the Bishops ' Palace ( Obispado ) and Federacion Redan . Units were shifted about , but were generally as follows : - 1 . ) the Black Fort : Col . Tyrore Uraga and 9 guns , - 2 . ) the Tannery : 2d Ligero ( Col . Jose M . Carrasco ) and Queretro ( Comdte . Jose M . Herrera ) Battalions and 3 guns ( 1 - 8 lb , 1 - 4 lb & 1 mtn . howitzer ) ( Lt Juan Expejo ) , - 3 . ) El Rincon : Lt . Col . Calisto Bravo and 3 guns ( Capt . Ignacio J . del Arenal ) - 4 . ) Purisima : Aguascalientes Battalion ( Col . Jose Ferro ) and one gun ( 1 - 12 lb ) ( Capt Patricio Gutierrez ) - 5 . ) Ft . Libertad and 4 guns , - 6 . ) Obispado : various units ( Lt . Col . Franciso Berra of Mexico Activos Bn ) ) and 4 guns , - 7 . ) Federacion Redan and 2 guns , and - 8 . ) the Reserves at la Plaza : 3d Ligero ( Lt . Col . Juan Castro ) and 1 gun ( 1 - 8 lb ) ( Lt Agustin Espinosa ) . General Zachary Taylor , commander of all U . S . forces , decided to attack western Monterrey in a giant " hook " movement while carrying out a small diversion against northeastern Monterrey . On September the 21st , William Jenkins Worth overran Federation Hill in western Monterrey , there was a light skirmish with the Mexican cavalry and the Jalisco ( Col . Juan Najera ) and Guanajuato ( Lt . Col . Mariano Moret ) lancers being replused with the commander of the former killed . In the mean time Taylor launched a diversion against eastern Monterrey . This diversion quickly grew into a full - out assault as Taylor threw half of his overall army against northeast Monterrey . In order to reach El Fortin de la Teneria the 1st Division under command of Brigadier General Worth had to pass through the areas of cannon fire from at least 4 other forts as they moved forward toward El Fortin Del teneria . Taylor ' s best infantry division was repelled by 200 Mexican soldiers in " El Fortin Del Teneria " ( Tannery Fort ) until the end of the day when his men finally managed to overrun the fort . Jefferson Davis ' s Mississippians and a Tennessee regiment under Colonel William Campbell stormed over its wall with bayonets and swords . On September 22 , 1846 , General Worth attacked a second more fortified hill called Independence Hill where an old Bishop ' s palace ( Obispado ) was located that contained 300 Mexican soldiers . Worth ' s men climbed the steep slopes of the hill , attacked a small redoubt , and tricked the Mexican soldiers inside the Bishop ' s Palace to advance out of the fort into the middle of hill , where they were attacked from both sides by Texan volunteers and from the middle by Louisiana volunteers and regular soldiers . On September 23 , General Worth advanced into the city from the west while Taylor moved his men into the city from the east . The Texan volunteers taught the U . S . regulars new techniques for fighting in the city ; techniques that they did not employ on the 21st which led to staggering casualties . Armed with these new urban warfare skills , the U . S . Army along with Texan , Mississippian , and Tennessee volunteers moved house to house , rooting out Mexican soldiers hiding on rooftops and inside the thick , adobe - walled houses of northern Mexico . The Mexican Army and the city ' s remaining citizens congregated in the city plaza . Trapped in the city plaza and bombarded by U . S . forces with howitzers , General Ampudia decided to negotiate . Taylor , still facing a larger army in enemy territory , negotiated a two month armistice in return for the surrender of the city . The Mexican Army was allowed to march from the city on the 26th , 27th and 28th of the month , with their arms and one battery of artillery ( six guns ) . Left behind were some 25 guns . Although it was considered another victory for the United States , the number of American and Mexican casualties were high . The Americans lost 120 with over 368 wounded / injured , the Mexican side lost 123 with over 325 wounded / injured . Both totals far more then in the 2 previous confrontations . Aftermath . The resulting armistice signed between Taylor and Ampudia had major effects upon the outcome of the war . Taylor was lambasted by some in the federal government , where President James K . Polk insisted that the U . S . Army had no authority to negotiate truces , only to " kill the enemy " . In addition , his terms of armistice , which allowed Ampudia ' s forces to retreat with battle honors and all of their weapons , were seen as foolish and short - sighted by some U . S . observers . For his part , some have argued that Ampudia had begun the defeat of Mexico . Many Mexican soldiers became disenchanted with the war . In a well - fortified , well - supplied position , an army of ten thousand Mexican soldiers had resisted the U . S . Army for three days , only to be forced into surrender by American urban battle tactics , heavy artillery and possibly further division in the Mexican ranks .