On May 1st, the opening salvos of the Battle of Chancellorsville were sounded. Union General Joseph Hooker attempted an ambitious double envelopment of Lee’s army. Unfortunately, such a move was beyond the communications technology of the day and resulted in confusion and delay. In the face of these movements, Lee divided his vastly out-numbered army, holding Sedgewick at Fredericksburg, and sending Stonewall Jackson’s corps on a wide flanking movement late in the day of May2nd. Jackson’s troops burst out of the woods, falling on the unprotected and unprepared flank of Oliver Howard’s 11th corps. The Union troops fled in panic, as they would do again at Gettysburg in July. Jackson’s corps advanced to within 1.25 miles of the Union headquarters, but the coming of darkness and the thick woods the southerners found themselves in created confusion. On the verge of completely routing the Army of the Potomac, Jackson’s troops were forced to stop and dig in. Later that night, Jackson and his staff, trying to ascertain where the lines were, advanced through the woods to within earshot of the Union lines. Returning, they were mistaken for Union cavalry. Troops of the 18th North Carolina fired, wounding Jackson. His right arm had been broken and was eventually amputated. During his recovery, he contracted pneumonia and died on May 10th. Despite what was an amazing victory for the vastly outnumbered Confederates, the loss of General Jackson amounted to a major defeat. The loss of his aggressive and intelligent leadership very likely led to defeat for Lee at Gettysburg.
On May 12th John Gregg’s Confederate Brigade attacked a Union Division in Raymond, MS between Vicksburg and Jackson. Gregg had secretly been outflanked and his forces were destroyed. The action completed the encirclement of Vicksburg. The next day, two Union corps under Sherman and McPherson advanced on Jackson, MS, which they took on May 14th.
From May 14-18, Lee, Jefferson Davis and the Confederate cabinet met to discuss the summer strategy for 1863. It was here that the fateful decision to invade the North through Maryland and Pennsylvania was made.
On May 15th, CSA General Joe Johnston ordered Pemberton to break out of Vicksburg. Pemberton refuses the order. Instead, he and Johnston together attack the Federal line near Champion Hill. The hill changes hands three times in pitched fighting, but the two southern forces fail to join and Pemberton is forced to fall back to Vicksburg. On the 17th, Pemberton had his men backed up to the Black River. When the Union attacked, the line broke with the southerners crossing the river before destroying the bridge. Grant’s forces seized the bridge intact and began to close on Vicksburg.
On the 19th, Sherman launches a full-scale frontal assault on the Vicksburg defenses. However, he is pushed back with heavy losses. Other Union assaults on the 22nd failed as well. Grant then decided to begin a siege of the vital Mississippi port city on the 26th.