Mexican–American War campaigns
At the conclusion of this conflict, the U.S. had added some one million square miles of territory, including what today are the states of Texas, Arizona, New Mexico, and California, as well as portions of Colorado, Wyoming, Utah, and Nevada.
These sectional and political differences ripped the fabric of the union of states and eventually contributed to the start of the American Civil War, just 13 years later.
Early in 1846, General Zachary Taylor built a fort on the Rio Grande opposite the Mexican town of Matamoros.
By the end of the month, General Taylor had become concerned about his lines of communication with his lightly held main base at Point Isabel, near the mouth of the Rio Grande.
Therefore, on May 1, Taylor moved the bulk of his army to Point Isabel, leaving a small detachment of artillery and infantry under Maj. Jacob Brown at the fort opposite Matamoros.
[3] The next morning, Taylor, continuing his advance, found the Mexicans a few miles down the road, where they had taken up a strong defensive position in a dry river bed known as the Resaca de la Palma.
In this second successive day of battle, the infantry conducted most of the action, although the dragoons played an important part in knocking out the enemy artillery.
The next objective was Monterey, but the direct overland route from Matamoros lacked water and forage; Taylor therefore waited until August for the arrival of steamboats, with which he moved his army 130 miles (210 km) upriver to Camargo.
Meanwhile, thousands of volunteers had poured into Matamoros, but disease and various security and logistic factors limited Taylor to a force of little more than 6,000 men for the Monterey campaign.
On September 24, Ampudia offered to surrender the city on the condition that his troops be allowed to withdraw unimpeded and that an eight-week armistice go into effect.
Taylor, believing that his mission was simply to hold northern Mexico, accepted the terms and the Mexican troops evacuated the city the following day.
Taylor was severely criticized in Washington for agreeing to the Mexican terms, and the Administration promptly repudiated the armistice, which had almost expired by the time the news reached Monterrey Meanwhile, in keeping with the strategic plan, the other two prongs of advance into northern Mexico had been put in motion.
Col. Alexander William Doniphan in command of the 850 men of the 1st Regiment of Missouri mounted volunteers advancing from Santa Fe, New Mexico won on Christmas Day 1846 the Battle of El Brazito (outside modern-day El Paso, Texas) and the Battle of the Sacramento, enabling the capture of the city of Chihuahua The third prong, Col. (later Maj. Gen.) Stephen W. Kearny's "Army of the West", a force of about 1,660 men, left Fort Leavenworth, Kansas early in June 1846 and captured Santa Fe, New Mexico unopposed on August 18.
At San Diego, Kearny joined Commodore Robert F. Stockton, who had replaced Sloat, and their combined force of some 600 men (volunteer militia, sailors, marines and Dragoons) after same minor skirmishing, re-occupied Los Angeles, California on January 10, 1847, with no casualties.
Three days later, the last remaining Californian opposition capitulated to the very generous terms in the Treaty of Cahuenga to the volunteer force of about 450 men commanded by Fremont.
Learning of the weakness of the American forces near Saltillo, Santa Anna moved with about 15,000 men to the attack in February 1847 across about 200 miles (320 km) of desert.
Santa Anna used French tactics in the Battle of Buena Vista, attempting to overwhelm American positions with dense columns of men.
Massed volleys of infantry fire and artillery proved effective against the attacking columns, and, after two days of the most severe fighting of the war, Santa Anna, declared victory and withdrew his dispirited army to San Luis Potosí, having lost from 1,500 to 2,000 men killed and wounded.
[6] On June 13, 1847, Commodore Perry assembled the Mosquito Fleet and began moving towards the Grijalva River, towing 47 boats that carried a landing force of 1,173.
[7] Scott's army, numbering 13,660 men, rendezvoused at Lobos Island late in February 1847 and, on March 2, sailed for Veracruz, convoyed by a naval force under Commodore Matthew C. Perry.
This first major amphibious landing by the U.S. Army was unopposed, the Mexican commandant general, Juan Morales, having decided to keep his force of only 4,300 men behind the city's walls.
The first resistance encountered was near the hamlet of Cerro Gordo where Santa Anna had strongly entrenched an army of about 12,000 men in mountain passes through which the road ran to Jalapa.
Scott quickly won the battle with a flanking movement that cut off the enemy escape route, and the Mexicans surrendered in droves.
Scott stayed at Puebla until the beginning of August, awaiting reinforcement and the outcome of peace negotiations which were being conducted by Nicholas P. Trist, a State Department official who had accompanied the expedition.
Scott boldly struck out for Mexico City on August 7, the negotiations having failed, abandoning his line of communications to the coast.
Scott first encountered stiff resistance at Contreras where the Mexicans were finally put to flight after suffering an estimated 700 casualties and the loss of 800 prisoners.
Santa Anna promptly made another stand on Churubusco where he suffered a disastrous defeat in which his total losses for the day—killed, wounded, and especially deserters—were probably as high as 10,000.
Santa Anna abdicated the Presidency, and the last remnant of his army, about 1,500 volunteers, was completely defeated a few days later while attempting to capture an American supply train.
In addition, diarrhea, dysentery and typhoid claimed lives amid the poor sanitation common to the army camps of this period.
[12] Polk had pledged to seek expanded territory in Oregon and Texas, as part of his campaign in 1844, but the regular army was not sufficiently large to sustain extended conflicts on two fronts.
