This army entered New Mexico along the traditional route, moving up the Rio Grande from El Paso. It quickly subdued the forts and Union troops in southern New Mexico and continued up-river. On February 21, 1862, it met a Union army commanded by Colonel E. R. S. Canby at Valverde, a small community about twenty miles south of Socorro, New Mexico. Kit Carson, New Mexico’s famous trapper and scout, commanded the New Mexico Volunteers, a part of the Union force. Canby’s troops were beaten and dispersed at the Battle of Val Verde, leaving the upper Rio Grande Valley virtually without defense. Within a few weeks, the Texans had taken Albuquerque and Santa Fe. But one stronghold in New Mexico remained in the hands of the Union forces. Fort Union, northeast of Las Vegas, New Mexico, became the focal point of action by both north and south. Sibley, marching from Santa Fe, knew success depended on the fall of Fort Union. The Union forces, equally aware of the importance of the fort, hurriedly reinforced it with a number of volunteers from Colorado. Within Fort Union, a crisis developed over differing opinions on strategy. The fort commander wanted to keep the garrison at full strength and fight the Confederates from within the fort. The Colorado Volunteers wanted to go out and meet the enemy. The latter won and a Union force moved into the passes of the Sangre de Cristo Mountains to meet the Confederates in a fateful battle that would decide control of the west. It was fought at Glorieta Pass on March 28, 1862. Despite the fact that the two armies met on this field, the contest was not decided there. Early on the morning of March 28, a force of 400 Colorado Volunteers, commanded by Colonel John M. Chivington, began a flanking action in hopes of hitting the Confederate rear. This group moved out of the Pass into the mountains, and by a very difficult route moved back toward the Pass behind the Confederate force. On a ridge overlooking Apache Canyon, they saw below them the entire Confederate supply train and cavalry horse herd. In a lightning hit-and-run attack, the supply train and horses were destroyed. When word of this reached Sibley at Glorieta Pass, there was little for him to do but to retire from the field. The Confederate force never recovered from this disaster and gradually retreated to Santa Fe, then back down the Rio Grande into Texas.