...hich Lieutenant McClellan took part. His company was then transferred to General Twiggs's division, and moved at its head, across the Pedregal, to Contreras. During the first day of the battle of Contreras (August 19), Lieutenant McClellan, while reconnoitring, ran into a Mexican regiment, and had his horse shot under him by a musket-ball. On the same day, while posting Magruder's battery, he had ano...