They passed after awhile into a narrow valley, down the center of which ran a dry arroyo, fully twenty feet deep, with perpendicular banks. The rest of the valley was crisscrossed with countless gullies worn by winter storms and floods, and the army was compelled to march in a slender file in the bed of the arroyo. Here many of the cavalrymen dismounted and led their horses. The cannon wheels clanked louder than ever. "I’ll be glad when we’re through this," said Bill Breakstone. "Seems to me the place was built for a trap, and it’s mighty lucky for us that there’s nobody here to spring it. Look out, Phil, you’d better watch your horse now! Some of these turnings are pretty rough, and you don’t want a thousand pounds or so of horseflesh tumbling down upon you." Phil came back from his visions and devoted himself to the task before them, one that required the full attention of every man. An entire battery became stuck in a gully that intersected the arroyo. He and other cavalrymen hitched their horses to the guns and helped pull them out. The whole army was now stumbling and struggling over the fearful ground. Every effort was made to save artillery and horses alike from injury. But as they approached its lower end the Pass of Angostura became still more difficult. The gullies increased in number, and many of the deep intersecting ravines ran far back into the mountains. A swarm of sure-footed skirmishers on either flank could have done great damage here to the Americans, but the peaks and the lava slopes on either side presented only silence and desolation. It was a long journey, difficult in the extreme, and attended by thousands of falls, cuts, and bruises, but the army came through the Pass of Angostura at last, marching out upon a series of promontories or ridges, each about a mile long and perhaps a third of a mile across. From these the exhausted troops looked back at the frowning mountains and the deep defile through which they had come. "That was certainly a job," said Bill Breakstone. "Yes," said Middleton, who stood near, "but what a place for a defense, the plateau and these promontories running out from it, and all the ravine and gullies behind!" It is a matter of chronicle that at least fifty officers were saying the same words at almost the same time, and even Phil, without military training, could see the truth of it. Taylor pushed on to Agua Neva, arriving there in the evening. But the next morning the reports of Santa Anna’s advance in overwhelming force became so numerous that he fell back with the main army to the mouth of the Pass of Angostura, leaving Marshall with his brave Kentuckians as a rear guard at Agua Neva, and with instructions to make the utmost resistance if they were attacked.