At the middle of November, Grant sent for Sherman to meet him at Columbus, Kentucky, bringing with him a good map of the country to the southward. At that meeting Grant explained his plans for the winter's campaign. His army now occupied the line from Memphis to Corinth, and he proposed to move at once against Pemberton, who was with the Rebel army near Holly Springs, behind the Tallahatchie River. He would personally move on Holly Springs, and McPherson would meet him there with the forces now at Corinth. Sherman was to leave a small garrison at Memphis, and lead the rest of his forces to meet Grant and McPherson. This movement against Pemberton was preliminary to the greater work of taking Vicksburg. The plan was carefully carried out. The three forces moved simultaneously against Pemberton, and at the same time General C. C. Washburne, under Sherman's orders, crossed the Mississippi with five thousand cavalry, from Helena, Arkansas, and marched toward Grenada, in the rear of Pemberton's army. This movement alarmed Pemberton, and he hastily abandoned his works and retreated to Grenada. Sherman joined Grant at Oxford, Miss., early in December, and then a dispatch came from Halleck, who was at Washington, urging Grant to proceed with the campaign against Vicksburg, with the aid of Porter's fleet and any other available assistance. Grant and Sherman discussed the proposed movement fully, and finally agreed upon a plan. Sherman was to be heavily reinforced at Memphis, and would have the co-operation of Porter's gunboats. He was to make a swift movement on the Yazoo, and take Vicksburg from the rear, while Grant, at Oxford, held Pemberton in check. Banks was then supposed to be moving up the river from New Orleans, and everything bade fair for the opening of the whole Mississippi. Sherman would have about forty thousand men, and would conduct the campaign almost entirely according to his own discretion, Grant's instructions to him being of the most rudimentary description. So he returned to Memphis and prepared for the work before him.