...burg, defeated and drove off about 6,000 men collected there to reinforce General Pemberton, under General Johnston, destroyed the railrords, and then turned and marched directly towards Vicksburg. General Pemberton only had the garrison of Vicksburg to operate against Grant after he crossed. He could only take 20,000 effectives out of the city to fight a battle, and the alternative was presented to him of eit...