This raid was made on the twelfth and thirteenth of June, and equipped with the detailed information secured by it Lee planned to assail McClellan on the twenty-sixth of June with a force sufficient to dislodge him from his besieging positions, to break his line of communication and supply by way of the White House on the York river, and to compel his retreat from the front of the Confederate capital to some point on the James river, where his gunboats could afford him needed protection. For the purposes of this operation Lee had a force somewhat inferior in men and guns to McClellan's, but not greatly inferior. On the other hand McClellan's army was badly placed, with half of it on the north and half of it on the south of the Chickahominy, neither half being within easy supporting distance of the other, while the line of communication and supply by way of the White House was peculiarly vulnerable in case of an attack from the rear. Reckoning upon these advantages, it was Lee's plan to have Jackson move down from Ashland, assail McClellan's right wing in flank and rear, drive back his forces and thus open the crossings of the river to the other Confederate corps, which were to cross one after the other and assail the enemy in front while Jackson should attack him in rear and flank. 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.