At the same time, besides these two combats which Scott had not expected, one planned by him was taking place. A few minutes after sending Twiggs toward Churubusco he ordered Pierce--and presently Shields also--to follow a road leading north from Coyoacán, cross Churubusco River, and move toward Santa Anna's rear, so as to protect the American flank and rear, favor the attack on the convent, and cut off the retreat of the Mexicans. The route adopted by the troops after leaving the road took them for a mile and a half through cornfields and marshes, and placed them near the highway, about three quarters of a mile north of the bridgehead, not far from the hacienda of Los Portales. To parry the blow Santa Anna at once moved in that direction with the Fourth Ligero, the Tulancingo regiment and most of the Eleventh Line, his finest corps, extending his men--perhaps 2200 in all--until they almost overlapped the Americans; while some 1500 or 2000 cavalry, probably consisting of the horse that had followed him to San Angel reinforced by that which had escaped from Contreras, menaced--though afraid to attack--Shields's left.[26.17] Precisely what occurred now cannot be stated, for apparently most of the reporting officers were more anxious to conceal than to disclose facts; but it seems clear that Shields handled the men clumsily, that his own regiments fell into disorder when charging and shrank from the devouring Mexican fire, and that Pierce's brigade, composed of excellent material but officered to a large extent with political favorites, actually skulked. The Mexicans, on the other hand, finding two ditches along the highway to protect them from the dreaded bayonet and an embankment to screen them somewhat from bullets, fought stiffly. Shields was therefore unable, with his six hundred good men and two small howitzers, to make any impression, and after a time his troops huddled wherever they could in the shelter of some buildings.[26.17]