Before the sun rose on July 3, the Federal Twelfth Corps attacked at the base of Culp's Hill to regain the ground that the Confederates had captured the previous day. By retaking these trenches, the Union Army had foiled Lee's hope of hitting the Union's right flank, so he concentrated his attack on what what would come to be known as Pickett's Charge. Confederate Maj. Gen. George Pickett was excited to make a name for himself because his division had missed much of the early action at Gettysburg. So, on the third day of the battle, he jumped at the chance to lead the Charge. The charge of 15,000 men was technically Longstreet's Charge (with Pickett's division and two of A.P. Hill's), but Pickett led the attack with his 5,500 soldiers.
Longstreet once again protested to Lee about the attack that morning, pointing out that the troops would have to cross an open field that was three-quarters of a mile long. The Union could watch them -- and fire at them -- from their vantage point on Cemetery Ridge. Lee, however, contended that the Union had almost been beaten the day before, and they would be too weak to sustain the charge in the center if the Confederate artillery bombarded the Union line. Whether this disagreement influenced Longstreet's handling of the day remains a point of debate among historians.
In the early afternoon, the Confederate and Union artilleries exchanged fire for about two hours, but the Union stopped firing early on. The Union's chief of artillery, Gen. Henry J. Hunt, correctly strategized that he could trick the Confederates into believing the Union didn't have enough firepower. But they actually had had plenty of reserve ammunition to fire as the Confederate troops crossed the open field.
Around 3 p.m., Longstreet ordered Pickett's three brigades, with Hill's six brigades behind him, to charge Cemetery Ridge. Historian James M. McPherson summed up it up this way: "Pickett's charge represented the Confederate war effort in microcosm: matchless valor, apparent initial success, an ultimate disaster" [source: McPherson]. Of the nearly 15,000 Confederates in the charge, only about half came back. Of the 5,500 men in Pickett's Division, 224 were killed, 1,140 wounded and 1,499 surrendered. He lost all 13 of his colonels.
In the end, only one Confederate brigade, Brig. Gen. Lewis Armistead's, made it to the top of the ridge. This is sometimes referred to as the "high-water mark of the Confederacy." Armistead was shot down by Union troops shortly after reaching the top. His best friend, Winfield Scott Hancock, who led the Union troops on Cemetery Ridge, was also seriously wounded in the battle.
Shortly after Armistead was shot down, Pickett's Charge mostly fell apart. With the Confederate troops repulsed, the Confederates who were able to stumble back across the field (without getting killed) regrouped disjointedly -- and eventually retreated.