I hesitate to add the tale of another Civil War battle onto the hallowed ground of Gettysburg, but the historical parallels almost beg for that story to be told here. In addition to ALTERNATIVE HISTORY, I contend that their is such a thing as PARALLEL HISTORY. For example, the story of Gettysburg as a battle at a crossroads town could be construed as a parallel to the siege at the crossroads town of Bastogne during the Battle of the Bulge in WW2.
In what can only be described as parallel history, the city of Vicksburg fell to Union forces on 4 July 1863! But the entire campaign that led to that victory has many parallels to that at Gettysburg. Just as GEN Robert E. Lee plunged his army deep into the North, MG Ulysses S. Grant was doing much the same hundreds of miles to the west. In a campaign that lasted weeks, he marched his army of 30,000 men across Arkansas and Louisiana targeting Vicksburg on the east bank of the Mississippi. In this case, the two events were not only parallel but occurred simultaneously. For the sack of brevity, I will oversimplify the campaign but the full story can be learned on-line.
https://en.wikipedia.org/wiki/Siege_of_Vicksburg#Confederate
Grant was on the west side of the mighty river, Vicksburg, also known as the Gibraltar or the Mississippi, was on the east bank, its bluffs heavily fortified and considered impregnable (think Singapore guarded from assault from the sea). For dozens of miles to the north, the terrain was swamp, impenetrable by an marching army. Grant had to march south until he could find a place to cross the Mississippi — no simple feat in its own right. How he got the ships there to accomplish that is a whole different chapter.
Once across the river, he had to march back to the north to besiege the city. Like Lee, he was now deep in Rebel territory with tenuous supply lines. He knew that it would be extremely difficult to establish a Medieval-like siege to such a large city. So first he cut off their supplies and in doing so replenished his. Like Lee sending Ewell to Carlisle, Grant sacked the nearby town of Jackson MS (the State capitol as was Harrisburg PA) through which came all of Vicksburg’s supplies, largely by rail. Grant took a major gamble in marching east and leaving the garrison at Vicksburg in his rear. He was betting that Confederate LTG John C, Pemberton would not leave the safety of the city to attack his rear. He won that bet!
The siege at Vicksburg lasted 40 days, it had begun actually before Lee made his northerly plunge — but Pemberton finally surrendered the city on 4 July 1863!
One other parallel point needs to be made. Being so deep in enemy territory. Grant was reluctant to take on thousands of prisoners of war, he paroled nearly 30,000 Rebels. This means that they were released upon signing a pledge not to re-join the fight. Not all lived up to that pledge. Grant would do the same at Appomattox when he allowed Lee and all his minions to return to their farms having to surrender only their muskets, not swords, sidearms nor horses.
With the fall of Vicksburg and the nearby Fort Donelson, the Union had complete control of the Mississippi. With a more secure supply line via the river, Grant marched east and south to target Mobile AL.
To this day, historians debate the merits of Gettysburg vs Vicksburg as to their relative importance in the ultimate victory of the Union over the CSA.
Grant’s victory at Vicksburg went a long way to his being appointed by Lincoln as overall Commander of all Union field forces. He became Meade’s commander. He then launched a three-pronged campaign to bring the CSA to its knees.