Grand Gulf was made the base of operations, and, well aware that reinforcements would be hurried to the garrison, Grant hastened his movements. While pressing his attack he learned that Johnston was at Jackson with a strong force, with which to reinforce Pemberton. He immediately dispatched McPherson and Sherman thither, and, after a fierce fight, Jackson was captured. Grant learned from deserters that Johnston, the chief Confederate commander in that section, had sent peremptory orders to Pemberton to leave Vicksburg and attack him in the rear. The latter, with his usual promptness, met this danger, and, by decisively defeating the enemy at Champion Hill, he accomplished the splendid feat of keeping Johnston out of Vicksburg and Pemberton in. It was a great exploit, for Jo Johnston was one of the ablest generals of the war, and the fine campaign which he had planned was brought to naught. Not only was he kept out of Vicksburg, but it was made impossible for him to send any help to Pemberton, around whom the Union commander was drawing the coils more tightly each day. [Illustration: GRANT AFTER THE BATTLE OF BELMONT.] Still the defenses of Vicksburg were too powerful to be captured by storm, and Grant did the only thing possible--he besieged the city. The siege began about the middle of May. The garrison had provisions for barely two months, from which they had to supply the inhabitants of the town. Jo Johnston saw the peril and set to work with such vigor to raise a force to send to the relief of Pemberton, that Grant was hurried into making an assault on the rebel works. This took place before daylight on the morning of May 19th. Though successful at first, the Federals were repulsed. A grand assault was undertaken three days later and pressed with the utmost bravery, but it resulted in another repulse, in which the loss of the assailants was three times greater than that of the defenders. Porter tried to help with his fleet, but his vessels were so badly injured by the batteries that they were compelled to withdraw from action. This failure showed that it was useless to try to capture Vicksburg except through a regular siege, which was pressed henceforth without intermission. Shells were thrown into the doomed city night and day; the people lived in caves, on short rations, and underwent miseries and sufferings which it is hard to comprehend in these days. All the time Grant was edging closer and closer. Parallels and approaches were constructed; mines sunk and countermining done. Several attempts were made to relieve Vicksburg, but the bulldog-like grip of Grant could not be loosened, and the condition of the garrison became much like that of Cornwallis at Yorktown in 1781. FALL OF VICKSBURG.