I enjoy reading about tactics and such, and when I toured the battlefield I wondered something. This being FR, I bet someone could give me an opinion.
The final charge aside, most of the casualties in the battle occurred in the wheat field and orchard. These to spots are relatively flat, open ground (except for a couple of farm houses near the orchard) and easily within range of the guns of either side. The Federals had high ground within a couple hundred yards of both. Whoever held them would basically become sitting ducks, as they didn’t look like keys to any important next move. Why did both sides expend so much sweat and blood to take an essentially worthless position? Was it because the two ends of the Federal line (Culp’s hill in the north and LRT in the south) were stalemated?
From the Union side the answer would be that Sickles had chosen a really unwise position, essentially in defiance of his orders.
When Longstreet attacked his position en echelon, it was thought too late for Sickles to retreat to Cemetery Ridge in an organized fashion without offering Longstreet an opportunity to breach this weak point in the Union line.
Hence the continual reinforcement of Sickles' Corps all day long and the continual struggle by the Union to push the Confederates far enough back past the Wheatfield and the Peach Orchard to allow the Union to reorganize its line without being breached.
From the Confederate point of view, it was a probing to find a weak point or a way to breach the Union line - given the way the day was going, every Confederate commander involved was justified in believing that one more assault, one more push, might create the opening they needed.
The hope was that Hood would turn the Union flank at the Round Tops and that McLaws might provide a pincers that would enable the Confederates to encircle the Union.
In short, it was the Union trying to plug the hole in its line all day and the Confederates trying to find the hole in the Union line all day.