Robert Underwood Johnson, Clarence Clough Buell, Battles and Leaders of the Civil War: The Opening Battles. Volume 1.

Prentiss's vigilance gave the first warning of the actual danger, and in fact commenced the contest. On Saturday, disquieted by the frequent appearance of the enemy's cavalry, he increased his pickets, though he had no evidence of the presence of a large force. Early Sunday morning one of these picket-guards, startled no doubt by the hum of forty thousand men half a mile distant, waking up for battle, went forward to ascertain the cause, and soon came upon the enemy's pickets, which it promptly attacked. It was then a quarter past 5 o'clock, and all things being ready, the Confederate general, accepting the signal of the pickets, at once gave the order to advance. Previously, however, General Prentiss, still apprehensive, had sent forward Colonel Moore of the 21st Missouri, with five companies to strengthen the picket-guard. On the way out Colonel Moore met the guard returning to camp with a number of its men killed and wounded. Sending the latter on to camp and calling for the remaining companies of his regiment, he proceeded to the front in time to take a good position on the border of a cleared field and opened fire upon the enemy's skirmishers, checking them for a while; but the main body forced him back upon the division with a considerable list of wounded, himself among the number. All this occurred in front of Sherman's camp, not in front of Prentiss's. This spirited beginning, unexpected on both sides, gave the first alarm to the divisions of Sherman and Prentiss. The latter promptly formed his division at the first news from the front, and moved a quarter of a mile in advance of his camp, where he was attacked before Sherman was under arms. He held his position until the enemy on his right passed him in attacking Sherman, whose left regiment immediately broke into rout. He then retired in some disorder, renewing the resistance in his camp but forced back in still greater disorder, until at 9 o'clock he came upon the line which Hurlbut and W. H. L. Wallace were forming half a mile in rear.

Upon the first alarm in his camp, which was simultaneous with the attack upon Sherman, McClernand rapidly got under arms, and endeavored to support Sherman's left with his Third Brigade, only two hundred yards in rear, while he placed his First and Second Brigades in inverted order still farther to the rear and left, to oppose the enemy's columns pouring in upon his left flank through the opening on Sherman's left; but his Third Brigade was forced back with the fugitives from Sherman's broken line by the advancing enemy, and endeavored with only partial success to form on the right of McClernand's line, which at first was formed with the left a little south, and the center north of the Corinth road. Before the formation was completed the line was compelled to retire by the pressure on its front and left flank, with the loss of 6 pieces of artillery, but it re-formed 300 yards in rear.

Hildebrand's brigade had now disappeared in complete disorder from the front, leaving three pieces of artillery in the hands of the enemy. Buckland formed promptly at the first alarm, and in order to keep the enemy back endeavored by Sherman's direction to throw a regiment beyond Oak Creek,