During the night, Lt. Zealous Bates Tower discovered a ravine running southwest from San Jerónimo to the rear of Valencia's camp, which Smith planned to use for a dawn attack the next morning. Lee volunteered to cross the Pedregal during the night so Scott could coordinate a diversion using Twiggs. Twiggs did so at 5 AM, just as Smith struck Valencia from the rear. Valencia did not put sentries along in the ravines along the path the American forces took, perhaps because of worries of desertion. When the attack came, Mexican forces resisted fiercely, but within seventeen minutes, Valencia and his force fled to San Ángel. Two of the cannons the American forces captured had been lost by Captain John P. O'Brien in bloody fighting at the Battle of Buena Vista in February 1847. The U.S. forces captured 22 pieces of artillery and four generals. The contemporary newspaper dispatch by George Wilkins Kendall names the generals: Miguel Blanco de Estrada, Manuel García Pueblita, N. Mendoza, and former President of Mexico and brigadier general José Mariano Salas, called "the notorious" for organizing the Guerrillas of Vengeance against the Americans. "Valencia's repeated refusal to follow orders had led to the dissolution of Mexico's most experienced and disciplined regiments and exposed the rest of the army to the same possibility."