The Union soldiers were not in a good situation. The infantrymen had walked dozens of miles across the hot Arizona desert, heading for the spring at Apache Pass, which was now blocked to them by the well-armed Chiricahua warriors. Low on water, and realizing a retreat back to Tucson without water could cost him many men, Roberts chose to fight. The Apaches had thrown up defenses, which consisted of several breastworks made of stone. They had also surprised the invaders with an ambush, waiting until the soldiers came within 30-80 yards of their positions before opening fire. Behind almost every mesquite tree and boulder hid an Apache with his rifle, six-shooter and knife. At first the Union troops could barely see their attackers. After a few minutes of intense combat Roberts ordered retreat, and his force withdrew to the mouth of Apache Pass. His men regrouped and unlimbered the mountain howitzers for an advance against the Apaches.