Grant, believing himself free to dispose of McClernand's new levies, had projected a combined movement by his own forces, marching by Grand Junction, and Sherman's, moving by water from Memphis, on the front and rear of Vicksburg.
Sherman set out from Memphis on the 20th of December in complete ignorance of Halleck's telegram of the 18th, conveying the President's positive order that McClernand was to command the expedition. Forrest cut the wires on the morning of the 19th just in time to intercept this telegram, as well as its counterpart, addressed to McClernand at Springfield, Illinois. On the 29th of December, Sherman met with the bloody repulse of Chickasaw Bluffs. On the 2d of January he returned to the mouth of the Yazoo, and there found McClernand armed with the bowstring and the baton.
Where was Grant? While his main body was still at Oxford, in march to the Yallabusha, Forrest, the ubiquitous, irrepressible Forrest, struck his line of communications, and, on the 20th of December, at the instant when Sherman was giving the signal to get under way from Memphis, Van Dorn was receiving the surrender of Holly Springs and the keys of Grant's depots. There seemed nothing for it but to fall back on Memphis or starve. Of this state of affairs Grant sent word to Sherman on the 20th. Eleven days later the despatch was telegraphed to Sherman by McClernand; nor was it until the 8th of January that Grant, at Holly Springs, learned from Washington the bad news from Sherman, then ten days old. As if to complete a very cat's-cradle of cross-purposes, Washington had heard of it only through the Richmond newspapers.
The collapse of the northern column, coupled with the Confederate occupation of Port Hudson, had completely changed the nature of the problem confided to Banks for solution. If he was to execute the letter of his instructions at all, he had now to choose between three courses, each involving an impossibility: to carry by assault a strong line of works, three miles long, defended by 16,000 good troops; to lay siege to the place, with the certainty that it would be relieved from Mississippi, and with the reasonable prospect of losing at least his siege train in the venture; to leave Port Hudson in his rear and go against Vicksburg, upon the supposition, in the last degree improbable, that he might find Grant, or McClernand, or Sherman there to meet him and furnish him with food and ammunition. This last alternative appears to have been the one towards which the government leaned, as far as its intentions can be gathered, yet Banks could only have accepted it by sacrificing his communications, putting New Orleans in imminent peril, and creating irreparable and almost inevitable disaster as a price of a remote chance of achieving a great success. In point of fact, in the early days of January, McClernand, accompanied by Sherman as a corps commander, was moving toward the White River and the brilliant adventure of Arkansas Post. After capturing this place on the 11th, McClernand meant to go straight to Little Rock, but Grant rose to the occasion and peremptorily recalled the troops to Milliken's Bend. "This wild-goose chase," as Grant not inaptly termed it, cost McClernand his new-fledged honors as commander of "The Army of the Mississippi," and brought him to Sherman's side as a commander of one of his own corps; a bitter draught of the same medicine he had so recently administered to Sherman.