James Duncan (September 29, 1811 – July 3, 1849) became a hero of the Mexican–American War for his capable command of an artillery battery at several important battles.

A promising career was cut short when he died of yellow fever on an inspection tour of Mobile, Alabama in 1849.

[1] He became a cadet at the United States Military Academy at West Point, New York on January 1, 1831, and graduated on July 1, 1834, as a brevet second lieutenant in the 2nd Artillery Regiment.

In 1838 he again served in the Second Seminole War before helping to supervise the Cherokee removal, part of the Trail of Tears.

[5] After months in camp, the first elements of the American army set out for Port Isabel, Texas which would serve as the forward base.

Late in the afternoon, the Mexicans launched an infantry and cavalry attack against the American left wing, but it was repulsed by Duncan's battery.

The Americans sustained losses of 34 killed and 113 wounded, but Mexican casualties were much heavier and included seven artillery pieces.

[2] In early January 1847, Taylor was ordered to transfer Worth's and Twiggs's divisions and two batteries, including Duncan's, to the army of Winfield Scott.

[12] Duncan fought at the Siege of Veracruz on March 9–29, 1847, at the Battle of Cerro Gordo on April 17–18, and at a skirmish in Amazoque on May 14.

Underestimating the strength of the Mexican position, Scott assigned the task of capturing the Molino to Worth's reinforced division, a total of 3,500 men.

Worth posted Clarke's brigade and Edwin Vose Sumner's 270 dragoons on the left, facing the Casa Mata fortification.

A force of Mexican cavalry and infantry appeared to the west, but it was driven off by the fire of Duncan's guns and pursued by Sumner's dragoons.

The Casa Mata repelled a second assault, but its defenders finally fled after a sustained bombardment by Duncan's battery.

Gideon Pillow, one of the U.S. division commanders, published an article that appeared in the New Orleans Delta and Picayune newspapers under the pseudonym "Leonidas".

On October 23, the Pittsburgh Post published a letter claiming that Worth and Duncan saved Scott from a blunder by convincing the commander-in-chief to use the southern approach to Mexico City.

[17] The Treaty of Guadalupe Hidalgo was signed on February 2, 1848, and Scott was recalled soon afterward, leaving Mexico in April.

[18] The court of inquiry was begun in Mexico City but was later transferred to Frederick, Maryland where Pillow was eventually acquitted.