The Thornton Affair — The First Bloodshed of the Mexican-American War

April 25, 1846–April 26, 1846

The Thornton Affair — also known as the Carricitos Skirmish — was fought between the United States of America and Mexico from April 25 to April 26, 1846, during the Mexican-American War. It was the first engagement of the war and opened the Texas Campaign. Mexican forces won the battle, which led to the United States Declaration of War against Mexico on May 12, 1846.

James K Polk, 11th President, Portrait

President James K. Polk. Image Source: National Portrait Gallery.

Thornton Affair Summary

The Thornton Affair was the first military engagement between the United States and Mexico in the Mexican-American War. It took place on April 25, 1846, at Rancho de Carricitos, on the north bank of the Rio Grande River. Mexican forces ambushed an American scouting party under the command of Captain Seth Thornton. The Mexicans routed the Americans, and took nearly 50 men as prisoners, including Captain William J. Hardee. When news of the incident reached Washington, President James K. Polk accused Mexican forces of attacking Americans on U.S. soil, and he asked Congress for a Declaration of War against Mexico. On May 12, 1846, the United States officially went to war with Mexico when the Senate voted 40-2 in favor of the Declaration of War.

Thornton Affair Facts

  • Also Known As: The Thornton Affair is also known as the “Thornton Skirmish” and the “Carricitos Skirmish.”
  • Date Started: The Thornton Affair started on April 25, 1846.
  • Date Ended: It ended on April 26, 1846.
  • Location: The Thornton Affair took place at Rancho de Carricitos, just east of present-day Bluetown, Texas.
  • Campaign: The battle was part of the Texas Campaign of the Mexican-American War.
  • Who Won: Mexico won the battle known as the Thornton Affair.
Thornton Affair, 1836, Illustration
This illustration depicts the Thornton Affair. Image Source: Pictorial History of the Mexican War (1850),

Thornton Affair History and Overview

During the Texas Revolution (1836–1836), Mexico believed the United States encouraged the uprising for the purpose of annexing Texas. After the Republic of Texas was established, Mexico threatened to declare war on the United States if it annexed Texas. As a result, the United States did not make any attempt to annex Texas until 1844. Texas was formally admitted to the Union on December 29, 1845, as the 28th state.

The Nueces Strip — Disputed Territory Between Mexico and the United States

Not only did the United States gain Texas, but it also inherited the ongoing border dispute between Texas and Mexico. Following the Battle of San Jacinto (1836), which ended the Texas Revolution, General Antonio López de Santa Anna agreed to the Treaties of Velasco. The treaties identified the Rio Grande River as the southern border of Texas. 

However, the Mexican Government never approved the treaties or recognized the independent Republic of Texas. As a result, Mexico insisted the southern border of Texas was the Nueces River, not the Rio Grande River. The disputed territory between the Nueces and the Rio Grande was known as the “Nueces Strip.”

When the United States annexed Texas in 1845, American officials hoped it would give them an opportunity to discuss the border with Mexico. However, it did not happen as Mexico cut off diplomatic ties with the United States.

The United States Army of Observation Moves into Texas

After Mexico cut off diplomatic relations with the United States, President James K. Polk ordered General Zachary Taylor to take command of an “Army of Observation.” Polk ordered Taylor to take the 3,500 men and march into Texas up to the Nueces River, on the border of the Nueces Strip. Taylor marched into Texas and established a camp at Corpus Christi, where the Nueces River flows into the Gulf of Mexico. From there, Taylor drilled and trained his men for seven months.

It is widely believed that Polk, a staunch believer in the idea of America’s Manifest Destiny, was looking to provoke Mexico into war with the United States. The purpose was to claim California, New Mexico, and the Nueces Strip. On March 8, 1846, ordered Taylor to cross the Nueces, into the Nueces Strip, down to the Rio Grande — which Texans and Polk claimed was the true southern border of Texas. 

Taylor and his men built Fort Texas near present-day Brownsville, Texas, on the north side of the Rio Grande. It was directly across from the town of Matamoros, Mexico. In response, Mexican General Mariano Arista demanded that Taylor withdraw from his camp and move back north of the Nueces River. However, Taylor refused the request and Arista marched his army toward Fort Texas.

General Zachary Taylor, Mexican American War
General Zachary Taylor. Image Source: Library of Congress.

Taylor Sends Thornton to Scout Mexican Forces

On April 24, General Taylor learned that Mexican troops had crossed the Rio Grande and were headed toward Fort Texas. Taylor responded by sending Captain Seth Thornton, a Mexican scout named Chapita, and more than 50 dragoons — mounted cavalry — up the river to verify the report and assess the strength of the enemy force. Thornton’s second-in-command for the mission was Captain William J. Hardee.

Thornton and his men traveled about 20-30 miles up the Rio Grande River. Along the way, they stopped at ranches and gathered information from local Mexicans. They arrived at Rancho de Carricitos early on the morning of April 25. 

When they arrived, they saw some men, who were Mexicans, working on buildings and approached them. However, when the men saw the Americans, they fled. The Americans chased after them. In their haste, Thornton neglected to leave guards at the entrance to the ranch.

The day before, General Anastasio Torréjon led 1,200 cavalry troops across the Rio Grande River at Las Rusias, a short distance upriver from Rancho de Carricitos. When he found out  Thornton was in the area, he moved to intercept the Americans. 

The Thornton Affair Begins

At Carricitos Ranch, Torréjon found the entrance unguarded and took advantage of Thornton’s mistake. He had some of his men surround the perimeter of the ranch, which was enclosed by a fence. Soon after, he received reinforcements of around 1,600 men, who he sent to the entrance to engage the Americans.

When Thornton and his men returned to the entrance, a skirmish broke out. When Thornton and his men realized they were outnumbered, they tried to charge the Mexican line but were met with heavy musket fire from all around. 

The Americans were trapped and surrounded by an estimated 2,500 Mexican troops on three sides —  with the Rio Grande River behind them. The situation was desperate, and they had no path to escape. The Mexican forces closed in and the Americans were forced to surrender. 

The Thornton Affair Ends

The fight came to an end with 11 of Thornton’s men dead, and 6 wounded. Most of the captured soldiers were taken to Matamoros as prisoners. However, some men, who were seriously injured, were sent back to the U.S. camp for medical treatment. 

Thornton escaped by jumping his horse over a tall fence, but his horse fell on him and he was pinned to the ground. The next day, Mexican troops found him and took him as a prisoner.

Mexican General Mariano Arista, commander in chief of Mexico’s Army of the North, argued the Americans were in Mexican territory. Because of that, the attack on Thornton and his men was justified.

Thornton Affair — Official Report by William J. Hardee

In the aftermath of the Thornton Affair, Captain William J. Hardee wrote an official account of the battle. Hardee was at Matamoros, Mexico when he wrote the report to Brigadier-General Zachary Taylor. Taylor was at his camp on the other side of the Rio Grande River, opposite Matamoros. 

Please note that section headings have been added, and text corrections have been made in order to improve understanding of Hardee’s report.

General William J Hardee, Civil War
Photograph of William J. Hardee, taken during the Civil War. Image Source: Wikipedia.

Matamoras, Mexico, April 26, 1846.

Sir — It becomes my painful duty to inform you of the circumstances which led to our being brought to this place as prisoners of war. Captain Thornton’s command, consisting of fifty-two dragoons, left camp, as you know, at night on the 24th instant; it marched 15 miles and halted until daylight when the march was again resumed. 

Thornton Gathers Information on the Mexican Movements

Captain Thornton’s orders, as I understood them, were to ascertain if the enemy had crossed the river above our camp, and to scout his position and force. All his inquiries on the way tended to the conviction that the enemy had crossed in strength. About 23 miles from our camp our guide became so satisfied of this fact that he refused to go any further, and no entreaties on the part of Captain Thornton could shake his resolution. 

Americans Arrive at Rancho de Carricitos

About three miles from this latter place we came to a large plantation bordering the river, and enclosed with a high chaparral fence, with some houses at its upper extremity. To these houses Captain Thornton endeavored, by entering the lower extremity, to approach; but failing to do so, he was compelled to pass around the fence, and entered the field by a pair of bars, the house being situated about 200 yards from the entrance. 

Americans Enter Rancho de Carricitos

Into this plantation the whole command entered in single file, without any guard being placed in front, without any sentinel at the bars, or any other precaution being taken to prevent surprise. Captain Thornton was prepossessed with the idea that the Mexicans had not crossed; and if they had, that they would not fight. 

Surrounded by Mexican Forces

I had been placed in rear, and was therefore the last to enter. When I came up to the house I found the men scattered in every direction, hunting for someone with whom to communicate. At last an old man was found; and while Captain Thornton was talking with him, the cry of alarm was given, and the enemy were seen in numbers at the bars. 

Thornton Orders the Charge

Our gallant commander, immediately gave the command to charge, and himself led the advance; but it was too late; the enemy had secured the entrance, and it was impossible to force it. The officers and men did everything that fearless intrepidity could accomplish; but the infantry had stationed themselves in the field on the right of the passage way, and the cavalry lined the exterior fence, and our retreat was hopelessly cut off. 

Americans Seek an Escape Route from Rancho de Carricitos

Seeing this, Captain Thornton turned to the right and skirted the interior of the fence, the command following him. During this time the enemy were shooting at us in every direction; and when the retreat commenced, our men were in a perfect state of disorder. 

Thornton’s Horse Runs Off

I rode up to Captain Thornton and told him that our only hope of safety was in tearing down the fence: he gave the order, but could not stop his horse, nor would the men stop. It was useless, for by this time the enemy had gained our rear in great numbers. Foreseeing that the direction which Captain Thornton was pursuing would lead to the certain destruction of himself and men, without the possibility of resistance, I turned to the right and told the men to follow me. 

Hardee Prepares for an Attack at the Rio Grande River

I made for the river, intending either to swim it or place myself in a position for defence. I found the bank too boggy to accomplish the former, and I therefore rallied the men, forming them in order of battle in the open field, and without the range of the infantry behind the fence. I counted twenty-five men and examined their arms, but almost every one had lost a sabre, a pistol, or carbine; nevertheless, the men were firm and disposed, if necessary, to fight to the last extremity. 

Hardee Offers to Surrender

In five minutes from the time the first shot was fired, the field was surrounded by a numerous body of men. However, I determined to sell our lives as dearly as possible if I could not secure good treatment, and accordingly I went forward and arranged with an officer that I should deliver myself and men as prisoners of war, to be treated with all the consideration to which such unfortunates are entitled by the rules of civilized warfare. 

I was taken to General Torrejon, who by this time had his whole force collected in the field. I found that some prisoners had already been taken; which, together with those I had and those which were subsequently brought in, amounted to 45 men, exclusive of Lieutenant Kane and myself. Four were wounded. 

I know nothing certain of the fate of Captain Thornton and Lieutenant Mason: the latter I did not see after the fight commenced. I am convinced they both died bravely. The former I know was unhorsed, and killed, as I learn, in single combat, Romano Falcon. Lieutenant Mason’s spurs were seen, after the fight, in possession of the enemy. The brave Sergeant Tredo fell in the first charge. Sergeant Smith was unhorsed and killed. The bodies of seven men were found, including, as I believe, the two officers above mentioned.

Captive Americans Taken to Matamoras

I was brought to Matamoras today about 4 o’clock, and I take pleasure in stating that since our surrender I and my brave companions in misfortune have been treated with uniform kindness and attention. 

Generosity and Kindness of the Mexicans

It may soften the rigors of war for you to be informed fully of this fact. Lieutenant Kane and myself are living with General Ampudia: we lodge in his hotel, eat at his table, and his frank, agreeable manner and generous hospitality almost make us forget our captivity. 

General Arista received us in the most gracious manner; said that his nation had been regarded as barbarous, and that he wished to prove to us the contrary. Told Lieutenant Kane and myself that we should receive half pay, and our men should receive ample rations, and in lieu of it for today 25 cents a piece. 

On declining the boon on the part of Lieutenant Kane and myself, and a request that we might be permitted to send to camp for money, he said no; that he could not permit it; that he intended to supply all our wants himself. These promises have already been fulfilled in part.

I am, sir, very respectfully, your obedient servant,


Captain 2d Dragoons.

Thornton Affair Significance

The Thornton Affair is important to United States history because President James K. Polk used it to justify asking Congress for a Declaration of War with Mexico.

On May 10, 1846, President Polk declared “Mexico has passed the boundary of the United States, has invaded our territory and shed American blood upon American soil.” He asked Congress for a formal Declaration of War. Congress agreed and voted to declare war on Mexico on May 12, 1846. 

By then, U.S. and Mexican troops had already engaged in the first two major battles of the conflict, at Palo Alto (May 8, 1846) and Resaca de la Palma (May 9, 1846). American forces, led by General Taylor, won both battles and secured the Rio Grande River as the southern border of the United States.

The Thornton Affair was followed by the Siege of Fort Texas (May 3–9, 1846).

Citation Information

The following information is provided for citations, including APA Style, Chicago Style, and MLA Style.

  • Article Title The Thornton Affair — The First Bloodshed of the Mexican-American War
  • Date April 25, 1846–April 26, 1846
  • Author
  • Keywords Thornton Affair, Mexican-American War, Seth Thornton, William J. Hardee
  • Website Name American History Central
  • Access Date May 30, 2024
  • Publisher R.Squared Communications, LLC
  • Original Published Date
  • Date of Last Update October 30, 2023