capture the city of Vicksburg, the principal Confederate stronghold along the Mississippi River. Grant made Sherman a corps commander and put him in charge of half of his forces. According to historian John D. Winters's The Civil War in Louisiana (1963), at this stage Sherman In December, Sherman's forces suffered a severe repulse at the Battle of Chickasaw Bayou, just north of Vicksburg. Sherman's operations were supposed to be coordinated with an advance on Vicksburg by Grant from another direction. Unbeknownst to Sherman, Grant abandoned his advance, and Sherman's river expedition met more resistance than expected. Soon after, Major General John A. McClernand ordered Sherman's XV Corps to join in his assault on Arkansas Post. Grant, who was on poor terms with McClernand, regarded this as a politically motivated distraction from the efforts to take Vicksburg, but Sherman had targeted Arkansas Post independently and considered the operation worthwhile. Arkansas Post was taken by the Union army and navy on January 11, 1863. The failure of the first phase of the campaign against Vicksburg led Grant to formulate an unorthodox new strategy, which called for the invading Union army to separate from its supply train and subsist by foraging. Sherman initially expressed reservations about the wisdom of these plans, but he soon submitted to Grant's leadership and the campaign in the spring of 1863 cemented Sherman's personal ties to Grant. The bulk of Grant's forces were now organized into three corps: the XIII Corps under McClernand, the XV Corps under Sherman, and the XVII Corps under Sherman's young protégé, Maj. Gen. James B. McPherson. During the long and complicated maneuvers against Vicksburg, one newspaper complained that the "army was being ruined in mud-turtle expeditions, under the leadership of a drunkard [Grant], whose confidential adviser [Sherman] was a lunatic". When Vicksburg fell on July 4, 1863, after a prolonged siege, the Union achieved a major strategic victory, putting navigation along the Mississippi River entirely under Union control and effectively cutting off the western half of the Confederacy from the eastern half. During the siege of Vicksburg, Confederate general Joseph E. Johnston had gathered a force of 30,000 men in Jackson, Mississippi, with the intention of relieving the garrison under the command of John C. Pemberton that was trapped inside Vicksburg. After Pemberton surrendered to Grant on July 4, Johnston advanced towards the rear of Grant's forces. In response to this threat, Grant