Skip to main content
Go to accessibility notice


    Contemporary Account of the "Thornhill Affair" and the Siege of Ft. Texas

    Complete Archive of Mexican War Letters From Army Surgeon Grayson M. Prevost. A spectacular archive of Mexican War letters chronicling the service of a young Army surgeon attached to General Zachary Taylor's army in northern Mexico. The collection totals about 92 letters comprising approximately 468pp., written by Dr. Prevost during the campaign to his father, mother, sisters and brother in Philadelphia. The letters are arranged chronologically, in plastic page protectors, and inserted into three large three-ring binders. The condition of the letters is unusually fine, especially in view of the difficult conditions under which many were written. The majority of the letters are written in ink with the exception of a very few in pencil and the vast majority are highly legible, the few exceptions being those written under difficult field conditions or as Prevost was recovering from illness. The letters bear datelines from many of the important villages and towns made famous during the campaign including Matamoras, Camargo, Saltillo, Monclova, Buena Vista, Monterey, and Zacatecas. Many of the letters are postmarked Point Isabel, Brazos (de Santiago), and New Orleans. Additionally, the collection includes a limited amount of biographical information about Dr. Prevost and a series of photocopies of letters obtained from the National Archives that he wrote to the Surgeon General of the Army seeking assignments prior to the beginning of the Mexican War. After graduating from The Medical Institute of Philadelphia in 1844, Prevost spends two years working as a civilian surgeon at various army posts including West Point.

    Prevost's keen observations are remarkably brought to life in his letters by his skillful writing style. The archive begins with a letter to his sister dated March 6, 1846 and ends with a letter to his brother dated February 17, 1849. Space limits a comprehensive accounting of each letter so, in an effort to convey the essence of Prevost's wartime experiences, two particularly historic examples will be quoted at length.

    In the build up to the war Prevost makes his way from Mobile to Galveston via steamship and then on to advance camps along the Rio Grande. In a long letter written opposite Matamoras and dated April 27, 1846 Prevost describes in great detail the historic skirmish later referred to as the "Thornton Affair" which became the primary justification for President Polk's declaration of war against Mexico: "I have now to tell a story more disgraceful to American arms than anything which has occurred since the beginning of the war of 1812. Three days ago intelligence was brought in by our spies that the Mexican troops were crossing in force 20 miles up the river. A squadron of Dragoons under the command of Capt. Thornton was immediately detailed for a reconnaissance with the following orders: 'Ascertain the fact of the crossing, how many crossed and where they have gone. Throw out 2 or 3 men in advance these may be sacrificed, but your command will be safe.' These instructions were sufficiently clear, but the officer detailed for this duty [Thornton] was incapable of properly performing it...he should never have been entrusted with so important a duty. Having arrived at a certain point on the river a large trail was crossed. The Mexican guide who accompanied our party, here refused to proceed further being convinced of the neighborhood of a large force. The party went in without him, going single file through the thick chapperelle [sic] without advanced guard and without flankers. Captain Hardie [sic] [William J. Hardee, later a Confederate general], a prudent and brave officer commanded the rear company. Proceeding in this way they came at length to a large field surrounded on three sides by a very strong chaperelle [sic] hedge, and enclosed on the 4th by river...Prudence would have suggested that the whole command be halted outside the field excepting a non-commissioned officer with 2 or 3 men...a strange infatuation let Capt. Thornton to go on with his whole force not even leaving a guard at the bars...the Dragoons dispersed in every direction without any regard to the commonest military this state they were found by Captain Hardie [sic] who entered the field last. He remonstrated with Capt. Thornton without effect. Suddenly the alarm was given and fire commenced from behind the hedges on every side. Capt. Thornton led his troops back to the bars as rapidly as possible - They were closed by a bustling array of bayonets and by Mexican Dragoons and Lancers. Calling on his men to follow, he galloped around the hedge under Mexican fire. Capt. Hardie [sic] perceiving the folly of the proceeding, rode up to him and advised that he should attempt to cut through the hedges, while some of his men were at work cutting with their sabers, others might cover them with their fire. Capt. Thornton's horse had however become unmanageable and ran with him wherever he pleased. Capt. Hardie [sic] took command called the men to follow him, and made for the river, determined to swim it and take the chances on the opposite shore. Unfortunately an impossible marsh prevented him from reaching it. He rallied his men, examined their arms under fire and found that most of them after discharging them has lost their carbines and pistols. Seven men were killed and 4 wounded, one of them has since died. Two officers of whom one was Capt. Thornton also killed...this unfortunate man met his death from the hands of Roman Falcon, leader of the rancheros. It is well for him that he met his fate thus, that he did not live to be disgrace..." [written four days later]: "It was ascertained...that Captain Thornton is neither dead or wounded but held prisoner in Matamoras. His horse fell with him, probably was shot. He fell under his horse & remained insensible for several hours...the opinions expressed concerning Capt. Thornton were derived from the report of Capt. Hardie [sic] - as Capt. Thornton is now ascertained to be living, - & as his conduct may be in the future subject of official inquiry above all he will probably write a report of his own, it is proper until then to withdraw any opinion which may have been formed concerning his sad affair...". In a letter written from a camp opposite Matamoras dated May 16, 1846 Prevost writes that "prisoners have been exchanged. Capt. Thornton among others has been sent over and put under immediate arrest to be tried for his conduct in the unfortunate affair already spoken of...".

    In a letter dated May 3, 1846 Prevost writes of his first taste of battle during the Siege of Ft. Texas: "Sunday May 3rd. is a day I shall not soon forget. General loud reports in quick succession caused me to sit up in bed almost to exclaim 'at last, it is possible', a peculiar whizzing, such as I never before heard quickly convinced me that we are now actually being cannonaded & that the balls were quite close to me. I have often wondered what my feelings would really be under these circumstances and think I can say with truth that I felt calm & acted coolly having dressed myself and buckled on my belt and sword. I left my tent, at this moment a ball with a burning fuse passed as it seemed close to me - it was a howitzer shell...Presently one man was brought to our surgery which was a tent pitched near the middle of the fort. He was killed, his skull smashed by round shot. His body was laid in an empty tent while we were engaged in dressing the slight wound of another of those vile fiery globes fell & burst within 5 yards of us having passed through one of the hospital tents which was filled with patients, during which part of its course fortunately it did not explode, it fell and exploded in the empty tent - in which we had placed the smashed our dead man into a jelly...The misfortune of our gallant Major Brown is the most deplorable event which has yet happened to us. On Wednesday morning while our men were working at the bomb proofs, Major Brown stood by directing and overseeing. Every few moments we were dodging & prostrating ourselves to escape the bursting shells. On one occasion as I was rising from the sand and dirt immediately after a shell had fallen without exploding, my ears were saluted with the cry - 'Doctor!', 'Doctor!', I turned around and saw Major Brown who had been standing near me, now supported in the arms of 2 men - his right leg shot off, the jagged ends of the bone sticking out, and from them the ragged muscle and skin hanging down and dripping with blood. Dr. McPhail assisted by Dr. Crittenden and myself immediately amputated the thigh. The operation was very neatly performed but owing to the miserable situation as regards care & treatment on which the patient has to be kept during the continuance of the bombardment the results is altogether doubtful." Major Brown later died of his wounds and the fort was renamed Ft. Brown in his honor.

    The remainder of the letters are no less interesting and while some are merely short pleasantries sent back to his family as his time permitted, nearly all of them contain some remarkable tidbit of information or observation. The archive is a trove of previously unpublished information that could make an important adjunct to the existing research on the Mexican-American war. Grayson M. Prevost was profoundly affected by his part in the war and these eloquent words, taken from one of his letters surely echo the experiences of soldiers in all wars, past and present: " little value is now set on human life - so little sympathy felt for human suffering. Indeed this is one of the worst features of war that it blunts, I trust only temporarily the finest of our natures, and produces strange feelings of indifferences to the misery of others, and even to our own misfortunes."

    Shipping, Taxes, Terms and Bidding
    Calculate Standard Domestic Shipping

    Sales Tax information  |  Terms and Conditions

    Bidding Guidelines and Bid Increments

    Glossary of Terms

    Auction Info

    Auction Dates
    June, 2008
    14th Saturday
    Bids + Registered Phone Bidders: 2
    Lot Tracking Activity: N/A
    Page Views: 685

    Buyer's Premium per Lot:
    19.5% of the successful bid (minimum $9) per lot.

    Sold for: Sign-in or Join (free & quick)

    Heritage membership

    Join Now - It's Free

    1. Past Auction Values (prices, photos, full descriptions, etc.)
    2. Bid online
    3. Free Collector newsletter
    4. Want List with instant e-mail notifications
    5. Reduced auction commissions when you resell your
    Consign now
    • Cash Advances
    • More Bidders
    • Trusted Experts
    • Over 200,000 Satisfied Consignors Since 1976
    Consign to the 2018 December 9 Civil War, Militaria, Arms & Armor - Dallas.

    Learn about consigning with us

    You reach a customer base that is in many ways completely unknown to the major auction houses, and your marketing to this base is as professional as one could hope for. As I continue to wind down my holdings.
    Michael Z.,
    Hawthorne, NY
    View More Testimonials receives more traffic than any other auction house website. (Source:

    Video tutorial

    Getting the most out of search

    Recent auctions

    2018 May 11 Space Exploration Signature Auction - Dallas
    2018 May 11 Space Exploration Signature Auction - Dallas
    REALIZED SO FAR $1,136,520