The next day, the Confederate Army awoke to find that the rest of the Union Army had arrived at Gettysburg. They were placed in position by Maj. Gen. Winfield Scott Hancock, who had been sent up a day earlier by Meade to command the battle. The Union's position was in the shape of a fishhook, curving around Culp's Hill in the North, snaking around Cemetery Hill, down the Cemetery Ridge and -- by the end of the day -- ending in a loop around Little Round Top.
Lee sent Ewell's corps to attack the Union right, around Cemetery and Culp's Hills. He then dispatched Longstreet's corps to attack the Union left, at the northern end of Cemetery Ridge. The plan was to first draw Union troops away from the left flank, leaving them vulnerable to Longstreet's attack. The Union would have to move its troops back to the left flank, leaving the right flank open to Ewell's full attack, causing both flanks to crumble.
Ewell's attack was delayed, as was Longstreet's, so the plan didn't take effect until late in the afternoon. Once again, Longstreet's approach is controversial -- some historians question if he intentionally moved slowly because he didn't believe in the plan. However, there is also some evidence that he was simply surprised by a Union commander, Daniel Sickles. Sickles, who was at the downward slope of Cemetery Ridge, felt exposed because he saw higher ground to his left. In an attempt to protect his flank, he moved his two divisions, including Brig. Gen. William Barksdale's Mississippi brigade, forward into an area known as the Peach Orchard. When Longstreet approached to attack Cemetery Ridge, he ran into Sickles a half mile in front of the ridge. This attack, which spread from the Peach Orchard to the nearby Wheat Field and Devil's Den, resulted in some of the worst fighting of Gettysburg.
As Barksdale's brigade broke through in the Peach Orchard, Meade's chief of engineers, Union Gen. Gouverneur K. Warren, realized that just beyond Sickles' position was the hill Little Round Top, which had prompted Sickles' move. If Longstreet's men got around Sickles, they could take Little Round Top and be in a position to fire on the Union line at will. Warren alerted Col. Strong Vincent, who placed his 20th Maine, led by Col. Joshua Lawrence Chamberlain, on Little Round Top. Chamberlain and his men withstood two hours of attacks. After losing more than a third of his men, Chamberlain ordered a bayonet charge that saved the Union flank -- this became one of the most famous events in the Battle of Gettysburg.
On the other side of Sickles, another regiment had to protect the gap he had created by moving forward. Maj. Gen. Hancock ordered the 262 men of the 1st Minnesota to slow the attack until reinforcements could arrive. Despite losing all but 47 men, the Minnesotans succeeded. Longstreet's men would continue in their attach, ending Gen. Edward Johson's assault on the Union left.
In all, each side lost more than 9,000 in casualties on the second day of the battle.
Lee decided that he had weakened the Union flanks enough that if he attacked the center the next day, it wouldn't be strong enough to withstand another attack. Longstreet didn't agree.