Answer:
hi from your options you gave in the comment sections to your question : There's was a lack of needed supplies for the army
There were no confederates in the area
He needed to begin operations south of the city
Grant moved his ships past Vicksburg because There were no confederates in the area
Explanation:
The batteries of the bluffs of the confederates on the River bank could outrun any union Naval ship crossing the Vicksburg hence Grant moved his troops south of the east bank of River Mississippi taking his men far away from the confederate lines and recrossing to the other side on a narrower part of the River which risked his ship been sunk
