The Battle of Valverde was fought in and around the town of Valverde in the New Mexico Territory. It was a major Confederate success in the New Mexico Campaign, despite having to leave later after the Battle of Glorieta Pass, which was a major Union victory.
Brig. Gen. Henry H. Sibley led his force of 2,500 men across the Rio Grande River and up the east side of the river to the ford at Valverde, north of Fort Craig, New Mexico, hoping to cut Union communications between the fort and military headquarters in Santa Fe. He planned to drive Union troops out of the New Mexico Territory and then capture Colorado before moving westward to California and the Pacific coast. Ultimately he hoped to annex the Mexican states of Chihuahua and Sonora, but first he had to capture Fort Craig, a Union fort on the west side of the Rio Grande River in south central New Mexico Territory.
Col. E.R.S. Canby left Fort Craig with more than 3,000 men to prevent the Confederates from crossing the river. Canby, "having no confidence in the militia and but little in the volunteers", resisted all temptation to come out of the fort and fight the Texans. Sibley realized the futility of assaulting the fort and decided his "only hope of success was to force the enemy to an open-field fight." When he was opposite them, across the river, Canby opened fire and sent Union cavalry over, forcing the Confederates back. The Confederates halted their retirement at the Old Rio Grande riverbed, which served as an excellent position.
After crossing all his men, Canby decided that a frontal assault would fail and deployed his force to assault and turn the Confederate left flank. Before he could do so, though, the Confederates attacked. Federals rebuffed a cavalry charge, but the main Confederate force made a frontal attack, capturing 6 artillery pieces and forcing the Union battle line to break and many of the men to flee. Canby quickly reorginized his men and ordered a retreat. Confederate reinforcements arrived and Sibley was about to order another attack when Canby asked for a truce, by a white flag, to remove the bodies of the dead and wounded.
Left in possession of the battlefield, the Confederates claimed victory but had suffered heavy casualties. Although the Confederates would soon occupy Santa Fe, they would have to leave the New Mexico Territory within 3-4 months, retreating to El Paso, Texas, what was the starting point of the campaign.
This battle represented Canby's low point in his career and Sibley's high point. Both men would go opposite direction in terms of reputation after the battle.