In mid-August 1847, the U.S. Army reached San Agustin, a small village on the outskirts of Mexico City. Unsure which road offered the least resistance, Scott sent Lee on a reconnaissance that revealed the best route was a trail that lay along the edge of a rugged, three-mile wide lava bed called the Pedregal. On August 19, while superintending a work party sent to widen the road, to make it passable for wagons and artillery, Lee skirmished with troops commanded by General Valencia, whose army was camped at Contreras, west of the Pedregal. Lee crossed the Pedregal on foot during the night to inform Scott. Lee then guided the reinforcements across the lava bed’s craggy terrain. After the battles of Contreras (Padierna) and Churubusco, Scott promoted Lee to the brevet rank of Lieutenant Colonel and called his actions at the Pedregal “the greatest feat of physical and moral courage performed by any individual, in my knowledge, pending the campaign.”