The plan miscarried in part. For once Jackson was not on time, and, after waiting for him until the afternoon of the twenty-seventh of June A. P. Hill grew impatient of the delay, and pushed his corps across the river at Meadow Bridge and, after a strenuous fight, drove the Federals out of Mechanicsville, without any help from Jackson. Longstreet and D. H. Hill at the lower crossings also grew impatient of delay, and without waiting for orders crossed and engaged the enemy. On the next morning Jackson was with them and he led the advance.
The plan of battle was that Jackson, with D. H. Hill for support, and keeping well in rear of McClellan's fortified positions, should push rapidly forward towards the York-river railroad, which constituted McClellan's sole line of communication and supply, while A. P. Hill and Longstreet, advancing upon Jackson's right, should attack McClellan in flank, front and rear whenever he might seriously oppose Jackson's movement.
There was some further miscarriage of plans, and in consequence of a delay in Jackson's advance Longstreet and Hill fell upon the right wing of McClellan's army posted in a strong strategic position at Gaines's Mills before the advance under Jackson was ready to strike its blow.
The Confederates here encountered a very obstinate resistance and they were not able to force the position until Jackson came up and joined in the assault. It was a critical moment of the war. Had McClellan been able to hold this position the Confederate campaign of offense must have completely collapsed, and with a superior force, the Federal general would have been free to conquer Richmond at that leisure which his engineering soul so greatly loved.
But with Jackson's force added to the commands of Longstreet and Hill, the Confederates, after a very determined and bloody contest, drove the Federals from their position and made themselves prospective masters of McClellan's sole line of communication with his only depot of supplies at the White House.
There was nothing now for McClellan to do but retreat as best he could to the James river at Harrison's Landing and make that, instead of the White House, a base of supplies. To do that was exceedingly difficult, as McClellan had open to him only one road and that a very bad one, while the Confederates on his flank had many roads by which to intercept and annoy his retreat.
During the course of that retreat, which was attended at every step by bloody contests, McClellan wrote in great bitterness of spirit to the Secretary of War in Washington (Mr. Stanton) on the twenty-eighth of June: "If I save this army now, I tell you plainly that I owe no thanks to you or to any other persons in Washington [obviously meaning Mr. Lincoln]. You have done your best to sacrifice this army."
McClellan, with an overwhelmingly superior force, had invested Richmond on the east and north. There he had strongly fortified himself. He had pushed his advance to within four miles of the Confederate capital. He had brought up tremendous siege guns and had apparently made himself complete master of the situation. Then Jackson, the two Hills, Longstreet and Ewell, under direction of Robert E. Lee, had fallen upon his flank and rear and had driven him out of one position after another with fearful slaughter, until his White House communication was cut off, and nothing remained to him but retreat to a new base on James river. The Confederates confidently calculated upon cutting off that retreat also and compelling the surrender of an army superior to their own in numbers, arms, resources and everything else except fighting ability.
This they would very probably have accomplished if McClellan had not developed in answer to a pressing need a fighting quality which he had not before shown, and his army a resolute determination to endure punishment such as none but the best of veterans are expected to show.
McClellan's one hope, one purpose, was to march his army out of the swamps and escape from the ceaseless Confederate assaults to a point on James river where the resistless fire of the gunboats might protect his men from further attack and give them a chance to rest. To that end, he retreated night and day, standing at bay now and then as the hunted stag does, and fighting desperately for the poor privilege of running away.