The topography of Virginia is favorable to an army menacing Washington, and unfavorable to one menacing Richmond. The fertile valley of the Shenandoah was inviting ground for soldiers. A Confederate force advancing down the valley came at every step nearer to the National capital, while a National force advancing up the valley was carried at every step farther away from the Confederate capital. The Confederates made much of this advantage, and the authorities at Washington were in constant fear of the capture of that city.
Soon after Stuart's raid, Lee began to make his dispositions to attack McClellan and drive him from the peninsula. He wrote to Jackson: "Unless McClellan can be driven out of his intrenchments, he will move by positions, under cover of his heavy guns, within shelling distance of Richmond." To convey the impression that Jackson was to move in force down the valley, Lee drew two brigades from his own army, placed them on the cars in Richmond in plain sight of some prisoners that were about to be exchanged, and sent them off to Jackson. Of course the released prisoners carried home the news. But Jackson returned with these reinforcements and Ewell's division of his corps, joined Lee, and on June 25th concerted a plan for immediate attack. Secretary Stanton appears to have been the only one that saw through the game; for be telegraphed to McClellan that while neither Banks nor McDowell nor Fremont could ascertain anything about Jackson's movements, his own belief was that he was going to Richmond. Yet the impression was not strong enough in the mind of the Secretary of War (or else the Secretary could not have his own way) to induce the appropriate countermove of immediately sending McDowell's whole corps to McClellan. General George A. McCall's division of that corps, however, had been forwarded, and on the 18th took a strong position on McClellan's extreme right, near Mechanicsville.
On the 25th McClellan had pushed back the Confederates on his left, taken a new position there, and advanced his outposts to a point only four miles from Richmond. but he began his movements too late, for the Confederates were already in motion. Leaving about thirty thousand men in the immediate defences of Richmond, Lee crossed the Chickahominy with about thirty-five thousand under Generals Ambrose P. Hill, Daniel H. Hill, and James Longstreet, intending to join Jackson's twenty-five thousand, and with this enormous force make a sudden attack on the twenty thousand National troops that were on the north side of the river, commanded by General Fitz-John Porter, destroy them before help could reach them, and seize McClellan's communications with his base.
Jackson, who was to have appeared on the field at sunrise of the 26th, was for once behind time. The other Confederate commanders became nervous and impatient; for if the movement were known to McClellan, he could, with a little boldness and some fighting, have captured Richmond that day. Indeed, the inhabitants of the city expected nothing else, and it is said that the archives of the Confederate Government were all packed and ready for instant removal. At midday General A. P. Hill's corps drove the small National force out of Mechanicsville, and advanced to McCall's strong position on Beaver Dam Crock. This they dared not attack in front; but they made desperate attempts on both flanks, and the result was an afternoon of fruitless fighting, in which they were literally mowed down by the well-served artillery and lost more than three thousand men, while McCall maintained his position at every point and lost fewer than three hundred.
That night, in pursuance of the plan for a change of base, the heavy guns that had thwarted Lee in his first attack were carried across the Chickahominy, together with a large part of the baggage-train. On the morning of the 27th Porter fell back somewhat to a position on a range of low hills, where he could keep the enemy in check till the stores were removed to the other side of the river, which was now his only object. McClellan sent him five thousand more men in the course of the day, being afraid to send any greater number, because he believed that the bulk of the Confederate army was in the defences on his left, and a show of activity there still further deceived him.
“Let us strengthen and cheer ourselves with the persuasion that nothing can befall us by chance, that all our times are in his hand, and that we are immortal till our work is done.”
–Works of Rev. William Jay, Evening, Sept. 12