Vicksburg should never have fallen.Pemberton should never have allowed Grant to sneak up on him, and that idiot Jefferson Davis should have sent support to prevent it. Yes, I know, many troops were busy in the East, but Vicksburg was a vital position. In my opinion, Pemberton lacked the will to stop the assault. Had he had the troops sent to encounter Grant as he crossed the Mississippi below Vicksburg, Grant would have been a sitting duck. Of course, it is always easy to be a back seat commander. If Joe Johnson had been in command, I think the results would have been different, but Davis disliked Johnson. As soon as Pemberton saw the gunboats passing by his fortifications, he should have taken the troops in the city and sent them south to encounter Grant as he crossed the river.
Actually General Joseph Johnson was in Command. President Davis had named him the Western theater commander. Johnson had 6,000 men at Jackson MS, when Grant attacked the city with two corps. Johnson withdrew and ordered Pemberton to try and join up with him. Pemberton army losing the battles of Champion Hill and Black River bridge to Grant, withdrew toward Vicksburg. President Davis told Pemberton that defending Vicksburg was to be his primary mission. Pemberton, caught between Johnson (his immediate commander) and Davis followed Davis’s orders and fell back to Vicksburg.