But the visiting official, after arriving at the front, soon learned that the army had complete confidence in its commander and that it would be a mistake to interfere with him. Indeed, by this time "the silent General," who had neither answered the numerous complaints against him nor paid the least attention to the storm of public indignation raging beyond his camp, had abandoned his efforts to reach Vicksburg from the front and was busily engaged in swinging his army behind it by a long overland route in the face of appalling difficulties, but with a grim resolution which forced all obstructions from his path. Meanwhile, the gun-boats under Admiral Porter were ordered to attempt to run the land batteries, and April 16, 1863, was selected as the date for their perilous mission. Each vessel had been carefully protected by cotton bales, and the crews stood ready with great wads of cotton to stop leaks, while all lights were extinguished except one in the stern of each ship to guide the one that followed. It was a black night when the Admiral started down the river in his flagship, and for a while it was hoped that the fleet would slip by the batteries under cover of darkness. The leading vessels did, indeed, escape the lookouts of the first forts, but before long a warning rocket shot into the sky and the river was instantly lit by immense bonfires which had been prepared for just this emergency, and by the glare of their flames the gunners poured shot and shell at the black hulls as they sped swiftly by. Shot after shot found its mark, but still the fleet continued on its course. Then, after the bonfires died down, houses were set on fire to enable the artillerists to see their targets, but before daylight the whole fleet had run the gauntlet and lay almost uninjured below Vicksburg, ready to coöperate with Grant's advancing army. By this time the Confederates must have realized that they were facing defeat. Nevertheless, for fully a month they stubbornly contested every foot of ground. But Grant, approaching the rear by his long, roundabout marches, handled his veteran troops with rare good judgment, moving swiftly and allowing his adversaries no rest, so that by the 17th of May, 1863, General Pemberton, commanding the defenses of Vicksburg, was forced to take refuge in the town. Grant immediately swung his army into position, blocking every avenue of escape and began a close siege. The prize for which he had been struggling for more than half a year was now fairly within his grasp, but there was still a chance that it might slip through his fingers, for close on his heels came General Joseph Johnston with a powerful army intent upon rescuing General Pemberton and his gallant garrison.