At this point on the Vicksburg, MS, battlefield in 1863 the Confederate forces held off an attack on the lines by the Union and when the Union troops withdrew with significant casualties Grant allowed a siege to begin a week into the battle on May 25th and it lasted until Vicksburg surrendered on July 4th, the day after Lee withdrew from Gettysburg in defeat. These are the twin events that the successful defense of the Union turned on - two long and bloody years of war had passed and two more to go but the outcome was decided on these two fronts.
