Immediately after the surrender of Vicksburg, Porter followed up the discomfiture of the Confederates by a series of raids into the interior of the country through its natural water-ways. Lieutenant-Commander Walker was again sent up to Yazoo City, this time in company with a force of troops numbering 5,000, under Major-General Herron. During the month that had passed since Walker's last visit, the enemy had been fortifying the place, and the batteries were found ready to receive the vessels. General Herron was then notified, and when his men were landed, a combined attack was made by the army and navy. The Confederates made but slight resistance and soon fled, abandoning everything. Six heavy guns and one vessel fell into the Union hands, and four fine steamers wore destroyed by the enemy. Unfortunately, while the De Kalb was moving slowly along she struck a torpedo, which exploded under her bow and sunk her. As she went down another exploded under her stern, shattering it badly. This gunboat, which at first was called the St. Louis, was the third to be lost of the seven. The Cincinnati was afterward raised; but the De Kalb was so shattered as to make it useless to repair her. At this same time Lieutenant-Commander Selfridge, with a force of light-draught gunboats, entered the Red River, turned out of it into the Black, and from the latter again into the Tensas; following one of the routes by which Grant had thought to move his army below Vicksburg. This water-line runs parallel with the Mississippi. Selfridge succeeded in reaching the head of navigation, Tensas Lake and Bayou Macon, thirty miles above Vicksburg, and only five or six from the Mississippi. The expedition was divided at a tributary of the Black, called Little Red River; two going up it, while two continued up the Tensas. Afterward it went up the Washita as far as Harrisonburg, where the batteries stopped them. Four steamers were destroyed, together with a quantity of ammunition and provisions. A few weeks later, in August, Lieutenant Bache, late of the Cincinnati, went up the White River with three gunboats, the Lexington, Cricket, and Marmora. At a second Little Red River, a narrow and crooked tributary of the White, the Cricket was sent off to look for two steamers said to be hidden there. Bache himself went on to Augusta, thirty miles further up the White, where he got certain news of the movements of the Confederate army in Arkansas; thus attaining one of his chief objects. He now returned to the mouth of the Little Red, and, leaving the Marmora there, went up himself to see how the Cricket had fared. The little vessel was met coming down; bringing with her the two steamers, but having lost one man killed and eight wounded in a brush with sharpshooters. On their return the three vessels were waylaid at every available point by musketry, but met with no loss. They had gone two hundred and fifty miles up the White, and forty up the Little Red River.