General Casey's pickets were but a short distance from camp, and they came streaming back in confusion, followed by the Rebels in masses. General Keyes saw that it was no feint, but an attack by an overwhelming force. He despatched a messenger to General Heintzelman, who was behind him towards Bottom's Bridge, for reinforcements. The firing became quick and heavy. General Sumner, three miles distant across the Chickahominy, heard it, and ordered his command under arms. The aide sent to Heintzelman lost his way in the woods, and was a long while in bearing the important message. Keyes saw that there was danger on Casey's left, south of the Williamsburg road, where the Rebels were appearing in great force, and he ordered Peck's brigade of Couch's division to advance and support Palmer. Spratt's battery, near Fair Oaks, opened upon the Rebels as they came through the woods on the right, supported by the Eleventh Maine, One Hundredth New York, One Hundred and Fourth Pennsylvania, and Ninety-Second New York. In the center, the One Hundred and Third Pennsylvania was sent forward to sustain the pickets, but quickly returned in confusion. The Rebel lines came into the open field, following the retreating pickets. All of Casey's guns opened with canister, and the fire was so severe that General Hill ordered his men to lie down, as it was impossible to advance in the face of such a storm.[24] General Hill dismounted from his horse, and criticised the fire of the different batteries. Longstreet's line was more than a mile in extent, and yet Huger and Whiting had not fired a cartridge. The fire was so terrible from the batteries, and from Palmer's, Wessell's, and Naglee's lines, that Longstreet changed his plan of attack, and, instead of advancing directly upon the center, attacked on both flanks. Some of his regiments filed towards the south, and crept through the bushes unseen by Casey. The others moved north, some in front of Naglee, and prepared to charge upon Spratt's battery. General Casey saw the plan. He rode along the line, called upon three of Naglee's regiments to drive the enemy into the woods. There was a rail-fence between the combatants, but the troops sprang over it with a cheer, formed in line, and fought the enemy face to face. The battle raged with great fury around the Oaks. [Footnote 24: Battle-Fields of the South, Vol. II. p. 4] The enemy was held in check a few minutes by the three regiments, but, being superior, advanced once more, firing as they came on. Naglee held his ground till the fighting was at close quarters,--till some of the Eleventh Maine were bayoneted. The order to retreat was given, and the lines fell back, followed closely by the enemy, who made a rush for Spratt's battery, and captured one of the guns.