It was not until the 25th of June that McClellan had definite knowledge of Jackson’s whereabouts. He was then located at Ashland, north of the Chickahominy, within striking distance of the Army of the Potomac. McClellan was surprised but he was not unprepared. Seven days before he had arranged for a new base of supplies on the James, which would now prove useful if he were driven south of the Chickahominy.

On the very day he heard of Jackson’s arrival at Ashland, McClellan was pushing his men forward to begin his siege of Richmond—that variety of warfare which his engineering soul loved so well. His advance guard was within four miles of the Confederate capital. His strong fortifications were bristling upon every vantage point, and his fond hope was that within a few days, at most, his efficient artillery, for which the Army of the Potomac was famous, would be belching forth its sheets of fire and lead into the beleagured city. In front of the Union encampment, near Fair Oaks, was a thick entanglement of scrubby pines, vines, and ragged bushes, full of ponds and marshes. This strip of woodland was less than five hundred yards wide. Beyond it was an open field half a mile in width. The Union soldiers pressed through the thicket to see what was on the other side and met the Confederate pickets among the trees. The advancing column drove them back. Upon emerging into the open, the Federal troops found it filled with rifle-pits, earthworks, and redoubts. At once they were met with a steady and incessant fire, which continued from eight in the morning until five in the afternoon. At times the contest almost reached the magnitude of a battle, and in the end the Union forces occupied the former position of their antagonists. This passage of arms, sometimes called the affair of Oak Grove or the Second Battle of Fair Oaks, was the prelude to the Seven Days’ Battles.

The following day, June 26th, had been set by General “Stonewall” Jackson as the date on which he would join Lee, and together they would fall upon the right wing of the Army of the Potomac. The Federals north of the Chickahominy were under the direct command of General Fitz John Porter. Defensive preparations had been made on an extensive scale. Field works, heavily armed with artillery, and rifle-pits, well manned, covered the roads and open fields and were often concealed by timber from the eye of the opposing army. The extreme right of the Union line lay near Mechanicsville on the upper Chickahominy. A tributary of this stream from the north was Beaver Dam Creek, upon whose left bank was a steep bluff, commanding the valley to the west. This naturally strong position, now well defended, was almost impregnable to an attack from the front.

Before sunrise of the appointed day the Confederate forces were at the Chickahominy bridges, awaiting the arrival of Jackson. To reach these some of the regiments had marched the greater part of the night. For once Jackson was behind time. The morning hours came and went. Noon passed and Jackson had not arrived. At three o’clock, General A. P. Hill, growing impatient, decided to put his troops in motion. Crossing at Meadow Bridge, he marched his men along the north side of the Chickahominy, and at Mechanicsville was joined by the commands of Longstreet and D. H. Hill. Driving the Union outposts to cover, the Confederates swept across the low approach to Beaver Dam Creek. A murderous fire from the batteries on the cliff poured into their ranks. Gallantly the attacking columns withstood the deluge of leaden hail and drew near the creek. A few of the more aggressive reached the opposite bank but their repulse was severe.

Later in the afternoon relief was sent to Hill, who again attempted to force the Union position at Ellerson’s Mill, where the slope of the west bank came close to the borders of the little stream. From across the open fields, in full view of the defenders of the cliff, the Confederates moved down the slope. They were in range of the Federal batteries, but the fire was reserved. Every artilleryman was at his post ready to fire at the word; the soldiers were in the rifle-pits sighting along the glittering barrels of their muskets with fingers on the triggers. As the approaching columns reached the stream they turned with the road that ran parallel to the bank.

From every waiting field-piece the shells came screaming through the air. Volley after volley of musketry was poured into the flanks of the marching Southerners. The hillside was soon covered with the victims of the gallant charge. Twilight fell upon the warring troops and there were no signs of a cessation of the unequal combat. Night fell, and still from the heights the lurid flames burst in a display of glorious pyrotechnics. It was nine o’clock when Hill finally drew back his shattered regiments, to await the coming of the morning. The Forty-fourth Georgia regiment suffered most in the fight; three hundred and thirty-five being the dreadful toll, in dead and wounded, paid for its efforts to break down the Union position. Dropping back to the rear this ill-fated regiment attempted to re-form its broken ranks, but its officers were all among those who had fallen. Both armies now prepared for another day and a renewal of the conflict.

The action at Beaver Dam Creek convinced McClellan that Jackson was really approaching with a large force, and he decided to begin his change of base from the Pamunkey to the James, leaving Porter and the Fifth Corps still on the left bank of the Chickahominy, to prevent Jackson’s fresh troops from interrupting this great movement. It was, indeed, a gigantic undertaking, for it involved marching an army of a hundred thousand men, including cavalry and artillery, across the marshy peninsula. A train of five thousand heavily loaded wagons and many siege-guns had to be transported; nearly three thousand cattle on the hoof had to be driven. From White House the supplies could be shipped by the York River Railroad as far as Savage’s Station. Thence to the James, a distance of seventeen miles, they had to be carried overland along a road intersected by many others from which a watchful opponent might easily attack. General Casey’s troops, guarding the supplies at White House, were transferred by way of the York and the James to Harrison’s Landing on the latter river. The transports were loaded with all the material they could carry. The rest was burned, or put in cars. These cars, with locomotives attached, were then run into the river.

On the night of June 26th, McCall’s Federal division, at Beaver Dam Creek, was directed to fall back to the bridges across the Chickahominy near Gaines’ Mill and there make a stand, for the purpose of holding the Confederate army. During the night the wagon trains and heavy guns were quietly moved across the river. Just before daylight the operation of removing the troops began. The Confederates were equally alert, for about the same time they opened a heavy fire on the retreating columns. This march of five miles was a continuous skirmish; but the Union forces, ably and skilfully handled, succeeded in reaching their new position on the Chickahominy heights.

The morning of the new day was becoming hot and sultry as the men of the Fifth Corps made ready for action in their new position. The selection of this ground had been well made; it occupied a series of heights fronted on the west by a sickle-shaped stream. The battle-lines followed the course of this creek, in the arc of a circle curving outward in the direction of the approaching army. The land beyond the creek was an open country, through which Powhite Creek meandered sluggishly, and beyond this a wood densely tangled with undergrowth. Around the Union position were also many patches of wooded land affording cover for the troops and screening the reserves from view.

Porter had learned from deserters and others that Jackson’s forces, united to those of Longstreet and the two Hills, were advancing with grim determination to annihilate the Army of the Potomac. He had less than eighteen thousand men to oppose the fifty thousand Confederates. To protect the Federals, trees had been felled along a small portion of their front, out of which barriers protected with rails and knapsacks were erected. Porter had considerable artillery, but only a small part of it could be used. It was two o’clock, on June 27th, when General A. P. Hill swung his division into line for the attack. He was unsupported by the other divisions, which had not yet arrived, but his columns moved rapidly toward the Union front. The assault was terrific, but twenty-six guns threw a hail-storm of lead into his ranks. Under the cover of this magnificent execution of artillery, the infantry sent messages of death to the approaching lines of gray.