The Battle of Molino del Rey turned out to be one of the bloodiest fights of the Mexican-American War. On September 6, 1847, as the armistice and peace talks that followed the Battle of Churubusco were breaking down, a large number of Mexican troops were observed around a group of low, massive stone buildings known as El Molino del Rey. Spread across the distance of this point, they were about 1,000 yards (1 km) west of the Castle at Chapultepec, which itself was about two miles (3 km) from the gates of Mexico City. A large grove of trees separated the molino from the castle.
General Winfield Scott received reports that the trees masked a foundry for casting cannon and there were rumors that Santa Anna, in desperate need of ordnance, was sending out church and convent bells to have them melted down and converted to cannon. Scott ordered Gen. Worth to attack and take the molino, break up the factory, and destroy any munitions found.
When there was no response to a brief bombardment, Worth assumed the Mexicans had abandoned the buildings. He sent an assault column of 500 men, the 8th Infantry led by Maj. George Wright, down a gently sloping plain. Behind them he placed Col. Charles F. Smith's light battalion and George Cadwalader's brigade in the center, and to their right Garland's brigade and a battery under Capt. Simon H. Drum. On the left was Col. James Duncan's battery and a brigade commanded by Bvt. Col. J. S. McIntosh. These men faced the Casa Mata, a stone structure adjacent to the molino. Worth had a total strength of 2,800 men.
When Worth's men arrived they met a fierce firefight. Six pieces of a field battery opened fire on them, while the heavy guns of Chapultepec and nearly 6,000 muskets from Mexican entrenchments mowed them down by the hundreds. At least half of Worth's men fell during the first barrage of bullets. Retreating, the Light Battalion and 11th Infantry sprang forward amid the clouds of smoke and deadly fire. The Mexicans' works quickly fell.