Final answer:
The Battle of Vicksburg was crucial in the Civil War because it gave the Union control over the Mississippi River, dividing the Confederacy and significantly impacting the war's direction towards a Union victory under General Ulysses S. Grant's leadership.
Step-by-step explanation:
The Battle of Vicksburg was a determining factor in the outcome of the Civil War because it secured the Union's control of the Mississippi River. This victory was essential for the Union's strategic plan of dividing the Confederacy and gaining a logistical advantage. Under the leadership of Major General Ulysses S. Grant, the Union forces engaged in a siege that eventually led to the Confederate surrender at Vicksburg. The fall of Vicksburg meant the Union controlled the entire Mississippi River, effectively splitting the Confederacy in two, which disrupted their supply lines and movement of troops. Furthermore, the capture of Vicksburg, along with the defeat of Confederate forces at Gettysburg, marked a significant turn in the war towards the Union's favor, from which the Confederate forces would never fully recover.