While Grant moved in this direction, Sherman started from Memphis, and another force was moved out from Helena to coöperate with him. Grant proceeded on the railroad, captured Holly Springs, and made it his depot of supplies, placing it in charge of Colonel Murphy. Continuing on his victorious path, the enemy abandoned Abbeville, and the line of the Tallahatchie, without a battle, and were finally driven into Grenada, with the Yallabusha River as their line of defence. Here the commander proposed to hold the rebels, and send an army from Memphis to make the direct attack upon Vicksburg. For this purpose Sherman was sent back, with directions to organize the expedition, and procure the coöperation of the squadron under Admiral Porter. Sherman executed his orders with his usual decision. With one hundred and twenty-seven steamers, and a flotilla of gunboats for his protection, he went down the river, and debarked his force at Johnston's Landing, near the mouth of the Yazoo. In the mean time, Van Dorn fell upon Holly Springs, surprised the garrison, and captured the place, with all the supplies which had been accumulated for the support of the advancing army. Colonel Murphy, in command, made no resistance whatever. By this sad and unexpected blow, inflicted by the imbecility or treachery of a single officer, the entire plan of the campaign was defeated. Grant, with his army, was in the heart of the enemy's country. His communications were cut in several places behind him; his base of supplies was lost, and his stores destroyed. The success of the experiment of subsisting upon the enemy had not been demonstrated then, and sorely chagrined and disappointed, the progressive general was obliged to retrace his steps. It was a bitter day to him. Murphy was promptly dismissed from the army, without even the formality of a court martial. Sherman, having no knowledge of the disaster which had crippled Grant, attacked the enemy's positions, and gained some advantages; but the rebels were reënforced by the withdrawal of the army in the rear of Vicksburg, and he reëmbarked his forces, abandoning the attempt. At this point General McClernand appeared, and superseded Sherman, who then took command of one of the corps of the army of the Mississippi, as it was from that time designated. The great bugbear of Grant's military existence, "a political general," was thrown into his path, and though this act of the president sorely grieved him, he made the best of the circumstances.