Union flags were placed also on the walls of the Great Redoubt and Second Texas Lunette, but it was at the Railroad Redoubt that a momentary breach was made in the Confederate defenses. Here, McClernand’s men reached the fort in force, and Sgt. Joseph E. Griffith and several comrades of the 22nd Iowa crawled through a gap in the wall, which had been blasted by Union artillery, and entered the outer works. All were shot down but Griffith. He was able to back out through the opening, bringing a dozen prisoners with him. When the Union assault threatened to engulf the fort, there was a call for Confederate volunteers to regain the lost ground. A volunteer company from the Texas Legion counterattacked and drove the Union troops from the outer defenses. [Illustration: _Union Battery Hickenlooper during the siege, within 100 yards of the Confederate line._ From a wartime sketch.] Encouraged by his partial success, McClernand asked Grant for reinforcements and a renewal of the attack which, he felt, would enable his men to break the Confederate line. Grant ordered Sherman and McPherson to commit their reserves and create a diversion in McClernand’s favor. The renewed assault was shattered by the resolute Confederate defense. It served only to increase Union losses and to intensify an already bitter controversy over McClernand’s military ability, which eventually resulted in his removal from command and the appointment of Maj. Gen. Edward Ord to head the XIII Corps. More than 3,000 Union soldiers lay dead or wounded in the ditches and on the slopes of the ridge. It was the last assault against Vicksburg. UNION SIEGE OPERATIONS. To bring the Union Army close against the Confederate defense line, construction of protected approaches was begun. As the siege progressed, “saps” or “approach trenches,” deep enough to conceal troops, zigzagged their way toward the works protecting Vicksburg. Ten major approaches were carried forward by pick and shovel details, each with a network of parallels, bomb proofs, and artillery emplacements. Over 60,000 feet of trenches and 89 artillery positions, mounting 220 guns, were completed. In the siege of Vicksburg “Spades were trumps.” A Federal infantryman was later to recall that Every man in the investing line became an army engineer day and night. The soldiers worked at digging narrow, zigzag approaches to the rebel works. Entrenchments, rifle pits, and dirt caves were made in every conceivable direction. When entrenchments were safe and finished, still others, yet farther in advance were made, as if by magic, in a single night. Other zigzag underground saps and mines were made for explosion under forts. Every day the regiments foot by foot, yard by yard, approached nearer the strongly armed rebel works. The soldiers got so they bored like gophers and beavers, with a spade in one hand and a gun in the other.