Under orders brought by McClernand the Army of the Tennessee was divided in four corps, known as the Thirteenth, Fifteenth, Sixteenth and Seventeenth, commanded respectively by McClernand, Sherman, Hurlbut and McPherson, Grant remaining commander of the whole. Sherman's corps formed the right wing, and consisted of the First Division, under General Steele, and the Second Division under General David Stuart, in the absence of Morgan L. Smith. Immediately upon arriving at Milliken's Bend, on January 4th, the expedition was sent on in the same boats, escorted by Porter's gunboats, to attack Arkansas Post, or Fort Hindman, an old settlement on the north bank of the Arkansas River, fifty miles from its mouth. This Fort was a very strong work, situated on a high bluff at the head of a horseshoe bend in the river. It was strongly armed and garrisoned by five thousand men under General Churchill, who had been directed to hold the place till his last man was dead. Sherman himself suggested the movement against this place, considering the capture of it necessary to the reduction of Vicksburg and freeing of the Mississippi. [Illustration: ADMIRAL DAVID D. PORTER.] On the night of January 4th Sherman and McClernand went into Porter's cabin on the Black Hawk, and discussed the expedition, asking Porter for his co-operation. Porter sat up in his bed and told them that he was short of coal and could not use wood for fuel. He addressed McClernand with a curtness amounting almost to discourtesy and Sherman watched his opportunity to get him to go into another room, and there asked him what he meant by it. Porter replied that he did not like McClernand, that he had long had a strong prejudice against him. Thereupon Sherman begged him, for the sake of the Union cause, to sink all personal feeling and do his best to work in harmony with McClernand. Porter promised to do so, and the discussion with McClernand was resumed. It was finally agreed that both McClernand and Porter were to go along with the expedition.