Battle of Molino del Rey The Battle of Molino del Rey was one of the bloodiest engagements of the Mexican - American War . It was fought in September 1847 between Mexican forces under General Antonio Léon against an American force under General Winfield Scott at a hill called El Molino del Rey near Mexico City . Background . On September 6 , 1847 , as the armistice and negotiations that followed the Battle of Churubusco were breaking down , a large number of Mexican troop s were observed around a group of low , massive stone buildings known as El Molino del Rey or King ' s Mill . Spread across the distance of this point , they were about 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 Mill from the castle , while the castle ' s batteries covered the area . General Winfield Scott received reports that the trees masked a foundry for casting cannon , and there were rumors that Antonio López de Santa Anna , leader of both the Mexican government and military , in desperate need of ordnance , was sending out church and convent bells to have them melted down and converted to cannon . From the roof of the bishop ' s palace at Tacubaya , where General Scott ' s quarters were , the evidence of there being some kind of furnace was distinctly visible in the bright red flame which rose above the Mill ' s roof . Scott ordered General Worth to attack and take the Mill , break up the factory , and destroy any munitions found . Battle . The King ' s Mill is a range of stone buildings , about fifteen hundred feet in length . These include a flour mill , and the old royal gunpowder mill . About five hundred yards from the northern extremity of the mills is the Casa Mata , another strong stone building . About three hundred yards west of Casa Mata is a large ravine , with the hacienda of Morales beyond . This range of ground , from the King ' s Mill on the left to the high ground west from the ravine , on the right , was occupied by the Mexican forces . In the mills were the National Guard Battalions of Liberty , Union , Querétaro , and Mina , under General Leon ( 1 , 400 men and 3 - 8 lb . guns ) , and the brigade of troops ( Grenaderos , San Blas Activos , Mixto de Santa Ana and Morelia Battalions ) commanded by General Joaquin Rangel . Between the mills and the Casa Mata were the 2nd light battalion , that of the Fijo the Mejico , and the 1st and 12th regiments of the line , with six pieces of artillery , under General Simeon Ramirez . In the Casa Mata were the 4th light battalion ( 600 men ) and 11th regiment of the line ( 900 men ) , under General Francisco Perez . In the grove of Chapultepec , in the rear of the mills , as a reserve , were the 1st and 3d light battalions ( 700 men ) . West of the ravine , toward Morales , were four thousand cavalry . With forces of 14 , 000 , General Santa Ana was confident of victory . At three o ' clock in the morning of September 8 , Worth sent an assault column of 500 men , the 8th Infantry led by Major George Wright , down a gently sloping plain . Behind them he placed Colonel Charles F . Smith ' s light battalion and George Cadwalader ' s brigade in the center , and to their right was Garland ' s brigade and a battery under Captain Simon H . Drum . On the left was Colonel James Duncan ' s battery and a brigade commanded by Colonel James S . McIntosh . Major Sumner commanded cavalry , initially on the extreme left . Worth had a total strength of 2 , 800 men . Captain Huger ' s heavy guns first opened fire on the mills , and continued until that point of the enemy ' s line became shaken . Major Wright ' s storming party dashed forward at a charge . Fire began from Mexican artillery on the flank of the column , and infantry on the flat roof of the mills opened fire from the flank as well as the front . Eleven of fourteen American officers were killed , but Smith and Cadwalader ' s forces occupied the enemy line in the center of the battle . Colonel Garland and Drum ' s battery occupied the enemy ' s position on the right , immediately under the guns of Chapultepec . On the left side , Colonel McIntosh ' s brigade advanced on the Casa Mata under murderous fire . McIntosh ' s forces compelled to fall back , Duncan ' s battery offered support and compelled the occupants and reinforcements to leave the Casa Mata . Aftermath . After blowing up the Casa Mata and destroying the molds and other property in the mills , American forces returned to Tacubaya . Three Mexican guns , large quantities of small arms and ammunition , and 800 prisoners were captured . Mexican forces lost over 769 casualties along with General Leon and Colonels Balderas ( Mina Battalion ) and Gelaty dead . American losses included 729 men killed and wounded , 49 officers wounded , and the deaths of Lieutenant - colonel Scott , Major Graham , Captains Merrill and Ayres , and Lieutenants Johnston , Armstrong , Strong , Shackelford , Burwell , and Farry . Preparations began immediately thereafter for the Battle of Chapultepec .