When Joseph Hooker crossed the Rapidan in late April 1863 to begin what became the Chancellorsville campaign, his plan called for Major General John Sedgwick to hold a separate force near Fredericksburg as a diversion. Sedgwick had the VI Corps, the I Corps, and John Gibbon's division of the II Corps. The VI and II Corps laid down pontoon bridges on April 29 and crossed the Rappahannock. The I Corps was ordered back west to reinforce Hooker's main army on the night of May 1. That left Sedgwick alone at the river with about 30,000 men. Lee, fighting Hooker fourteen miles to the west, had left Jubal Early to hold the city with about 12,000 men and 45 cannons - a tenth of the force the Union had used in December but enough to hold the same high ground that had broken the Union assault before. On the evening of May 2, Sedgwick received orders to attack Early.

Early's orders from Lee were clumsy. If Sedgwick attacked and won, Early was to retreat south. If Sedgwick moved west to reinforce Hooker, Early was to leave a covering force and follow. On May 2, Early misread the orders. He pulled most of his troops away from Fredericksburg toward Chancellorsville. Lee discovered the mistake and sent a corrective order; Early hurried back to his positions during the night before Sedgwick noticed. By dawn on May 3 the Confederate line was thinly stretched across Marye's Heights, with William Barksdale's Mississippi brigade holding the wall and the sunken road that had been the killing ground of the December battle. Cadmus Wilcox's brigade arrived during the day to reinforce. Even at full strength the Confederate line had a serious vulnerability on its right flank, where the ground sloped away and the trenches were shallow.

At dawn on May 3, Sedgwick moved his forces through Fredericksburg toward the heights. His first attack aimed at the ends of Marye's Heights, but a canal and a stream channeled his troops into killing zones. He pulled back. Next he sent John Newton's division straight at the center, where Barksdale's brigade held the stone wall. That attack also failed. Then the truce happened. The 7th Massachusetts officer asked Colonel Griffin of the 18th Mississippi for time to collect wounded; Griffin granted it; Union soldiers used the time to look at the Confederate right flank from up close. Sedgwick gathered elements from all three VI Corps divisions and threw them at the flank and the front simultaneously. The line broke. The first Union soldiers over the stone wall came from the 5th Wisconsin and the 6th Maine Infantry regiments. The 18th and 21st Mississippi - Griffin's regiment among them - were captured. Barksdale fell back to Lee's Hill and then withdrew south. The whole engagement lasted barely longer than the December battle's worst single assault.

Confederate casualties came to about 700 men and four cannons. Sedgwick had lost 1,100 of his own. Early withdrew his division two miles south while Wilcox retreated west, slowing Sedgwick's progress and giving Lee time to detach two divisions from his main army to deal with the threat from the east. Sedgwick, following his earlier orders, started west along the Plank Road to join Hooker at Chancellorsville. He never arrived - Lee's reinforcements stopped him at Salem Church the next day. Behind the lines, an argument erupted between Early and Barksdale after Early wrote a newspaper letter that Barksdale read as a slight to his Mississippi brigade. The two generals went back and forth in print until Lee, exhausted by both of them, ordered them to stop. Colonel Griffin survived the capture and lived to be paroled and exchanged. The 18th Mississippi was reconstituted but never recovered its strength.

The Second Battle of Fredericksburg is sometimes called the Second Battle of Marye's Heights, because that ridge is the ground where everything that mattered happened. The stone wall and sunken road are preserved today as part of Fredericksburg and Spotsylvania National Military Park. A short section of the original wall still stands; a longer restored section runs along the same alignment. The Innis House, just behind the wall, still carries the bullet holes from both battles. Fredericksburg National Cemetery sits on the heights above. From the air the battlefield reads as a strip of preserved green at the western edge of downtown Fredericksburg, the Rappahannock curving past to the east. The Union assault came uphill from the river plain; the same plain is now city streets. The colonel who allowed the truce, the soldiers who used it to map the flank, the Mississippians who were captured - all of them belong to a battle that the December slaughter has mostly drowned out.