text: Overall, the battle was a Union tactical victory, in which the Confederates suffered significant casualties and achieved none of their specific objectives due to the seriously flawed execution of Lee's plan. Instead of over 60,000 men crushing the enemy's flank, only five brigades, about 15,000 men, had seen action. Their losses were 1,484 versus Porter's 361. Despite the short-term Union success, however, it was the start of a strategic debacle. McClellan began to withdraw his army to the southeast and never regained the initiative.
  Gaines's Mill
  By the morning of June 27, the Union forces were concentrated into a semicircle with Porter collapsing his line into an east–west salient north of the river and the four corps south of the river remaining in their original positions. McClellan ordered Porter to hold Gaines's Mill at all costs so that the army could change its base of supply to the James River. Several of McClellan's subordinates urged him to attack Magruder's division south of the river, but he feared the vast numbers of Confederates he believed to be before him and refused to capitalize on the overwhelming superiority he actually held on that front.
  Lee continued his offensive on June 27, launching the largest Confederate attack of the war, about 57,000 men in six divisions. A.P. Hill resumed his attack across Beaver Dam Creek early in the morning, but found the line lightly defended. By early afternoon, he ran into strong opposition where Porter had deployed along Boatswain's Creek; the swampy terrain was a major obstacle to the attack. As Longstreet arrived to the south of A.P. Hill, he saw the difficulty of attacking over such terrain and delayed until Stonewall Jackson could attack on Hill's left.