River Skirmish Sparks Mexican-American War (25 APR 1846)

Courtesy Photo | “Captain Thornton’s Skirmish with the Mexicans,” from John Frost’s Pictorial History of Mexico and the Mexican War, 1848.  

UNITED STATES

04.19.2024

Story by Erin Thompson 

U.S. Army Intelligence Center of Excellence

by Erin E. Thompson, USAICoE Staff Historian

RIVER SKIRMISH SPARKS MEXICAN-AMERICAN WAR
On 25 April 1846, Capt. Seth B. Thornton led two companies of the 2d Dragoon Regiment to investigate reports of Mexican insurgents crossing into American-claimed territory. The resulting skirmish, known as the Thornton Affair, sparked the Mexican-American War in what became the American Southwest.

When Mexico gained independence from Spain in 1821, it granted settlement permissions to a number of Americans in the present-day state of Texas. As more families arrived there, the Mexican government began to fear the Americans would annex the region into their own borders. Tensions began rising between these Texan settlers and the Mexican government, sparking the Texas Revolution in 1835. Six months later, Texas declared independence from Mexico.

Over the next few years, the U.S. was unwilling to risk further bloodshed by annexing the land. Not until 1843 did President John Tyler’s government begin discussions to that end, and Texas became a state in December 1845. However, a major dispute remained over the state’s border with Mexico, with the Rio Grande serving as a point of contention between the nations.

After several failed political talks between the U.S. and Mexico, Gen. Zachary Taylor, commander of the U.S. Army of Occupation at Fort Jesup, Louisiana, was sent to the Rio Grande in spring 1846. He camped originally in Corpus Christi but later began building a fort on the bank of the Rio Grande opposite Matamoros, Mexico, where the Mexican Division of the North under Gen. Mariano Arista was stationed. Taylor’s fort was originally known as Fort Texas, but later changed to Fort Brown (current day Brownsville, Texas).

On 24 April 1846, General Taylor received word that a large unit under General Arista’s command was spotted crossing the Rio Grande about fourteen miles west of Matamoros. Taylor directed Captain Thornton to take two companies of the 2d Dragoon Regiment—between 55-70 men—to reconnoiter the area. Second in command was Capt. William J. Hardee, who later served as a Confederate lieutenant general. Thorton’s patrol left the night of 24 April.

On 25 April, the companies received mixed reports from their interrogations of residents living along the Rio Grande. Testifying of the incident later, 2d Lt. Elias Kent Kane, Jr., noted, “some [civilians] would say that they [Mexican forces] had crossed, and others that they had not.” The patrol was ultimately led to a corral at Rancho de Carracitos on the riverbank. They were summarily encircled by an enemy force numbering about 1,600 men commanded by Gen. Anastasio Torrejón.

The ambush was swift. Eleven dragoons from Thornton’s command died, several more were wounded, and the rest were taken prisoner by the Mexicans. News of the skirmish reached General Taylor from Thornton’s guide on the morning of 26 April. This was confirmed a few hours later by the arrival of an injured dragoon with a note from General Torrejón that his fort had no medical supplies to care for the wounded. The ambush of Thornton’s patrol outraged General Taylor, who sent word to President James K. Polk that “hostilities may now be considered commenced.” The Mexican-American War had finally begun.

Thornton, Hardee, and the rest of the prisoners were exchanged a few weeks later after the Battle of Resaca de la Palma. Thornton faced a court martial upon his return based on the accounts of Hardee and other dragoons about his handling of the patrol and attack. He was acquitted and returned to duty shortly after. He later died during the final engagement of the conflict at the Battle of Churubusco on 20 August 1847.


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• Date Taken: 04.19.2024
• Date Posted: 04.19.2024 14:16
• Story ID: 468971
• Location: US