The third day of the Battle of Gettysburg is when Confederate Gen. Robert E. Lee ordered a massive assault on the Union's front at Cemetery Ridge, which became known as Pickett's Charge.

After a thundering artillery barrage that was designed to soften the Union center but didn't have much impact because it was off target, twelve thousand Confederates, led by Gen. George Pickett marched across an open field toward the union lines. The Rebels were cut down as they walked and only 600 actually reached the Union line. In less than an hour, there were 6,800 casualties.

A Pickett's Charge Commemorative March will be held at 3 p.m. today. Nine National Park Rangers lead groups representing each of the Confederate assaulting brigades, and three National Park Rangers will assemble groups where men of three Union divisions awaited the attack. The march will end with the playing of Echo Taps.

Watch this event unfold on a live battlefield camera.