it might be as many as 10,000 men. With his men fatigued and operating in a thunderstorm, he withdrew most of his line, except for the 6th Missouri State Militia Cavalry, which continued skirmishing throughout the night. Fagan informed Price of the action, and the Confederates began retreating about midnight. Battle At around 01:00 the next morning, Curtis was informed that Sanborn had disengaged. Wishing to continue to press Price, he ordered Sanborn to attack at daybreak. Curtis had some of his staff officers assist Sanborn, who had been at least partially stymied by lack of staff assistance. An artillery battery was deployed at this time. Around 02:00, Fagan and Shelby withdrew their troops, and Marmaduke aligned his division to serve as a rearguard; it was over 2,000-strong. Marmaduke withdrew his main force south of the river, but left a skirmish line on a pair of mounds that were tall. During the night, part of the 2nd Colorado Cavalry broke through the Confederate skirmish line before withdrawing again. A Missouri State Militia unit and the 4th Iowa Cavalry also advanced under cover of darkness. During the night, Sanborn was reinforced by elements of Lieutenant Colonel Frederick W. Benteen's cavalry brigade. One of Benteen's regiments was detached to guard a river crossing to the north to prevent a Confederate flanking attack. At 04:00, Sanborn's artillery, six 3-inch ordnance rifles, opened fire on the Confederate line. At daybreak, the 4th Iowa Cavalry on the Union right attacked, using the broken ground as cover. Union artillery fired on the mounds, but despite aiming at a 15° elevation, overshot the elevated Confederate positions. Some of the misses struck the Confederate camp, accelerating its evacuation. Confederate marksmanship at that portion of the line was very poor, and the Iowans easily took the position, which consisted of one of the mounds. The 6th and 8th Missouri State Militia Cavalry Regiments attacked on the other end of the line. Again, the fire from the Confederate defenders was ineffective. Both sides were hampered by the rough terrain. The Confederate commander facing the two militia cavalry regiments feared being isolated from Marmaduke's main body on the other side of the river, so the mound was abandoned. The retreat was not detected until after the position had been completely abandoned. The historian Kyle Sinisi wrote that casualties during this stage of the fighting "appear to have been almost nonexistent". With