December 12 dawned cold and foggy. Burnside began pouring reinforcements into the city but made no effort to organize an attack. Instead, the Northerners squandered the day looting and vandalizing homes and shops. A Connecticut chaplain left a graphic account of some of this shameful behavior:
I saw men break down the doors to rooms of fine houses, enter, shatter the looking glasses with the blow of the ax, [and] knock the vases and lamps off the mantelpiece with a careless swing ... A cavalry man sat down at a fine rosewood Piano ... drove his saber through the polished keys, then knocked off the top [and] tore out the strings ...
The Battle of Fredericksburg would unfold in a natural amphitheater bounded on the east by the Rappahannock River and on the west by the line of hills fortified by Lee. When Jackson's men arrived from downstream, Longstreet sidled his corps to the north, defending roughly five miles of Lee's front. He mounted guns at Strong points such as Taylor's Hill, Marye's Heights, Howison Hill, and Telegraph (later Lee's) Hill, the Confederate command post. "Old Pete's" five divisions of infantry supported his artillery at the base of the slopes.
Below Marye's Heights a Georgia brigade under Brigadier General Thomas R. R. Cobb poised along a 600-yard portion of the Telegraph Road, the main thoroughfare to Richmond. Years of wagon traffic had worn down the surface of the roadway lending it a sunken appearance. Stone retaining walls paralleling the shoulders transformed this peaceful stretch of country highway into a ready-made trench.
Jackson's end of the line possessed less inherent strength. His command post at Prospect Hill rose only 65 feet above the surrounding plain. Jackson compensated for the weak terrain by stacking his four divisions one behind the other to a depth of nearly a mile. Any Union offensive against Lee's seven-mile line would, by necessity, traverse a virtually naked expanse in the teeth of a deadly artillery crossfire before reaching the Confederate infantry.
Burnside issued his attack orders early on the morning of December 13. They called for an assault against Jackson's corps by Major General William B. Franklin's Left Grand Division to be followed by an advance against Marye's Heights by Major General Edwin V. Sumner's Right Grand Division. Burnside used tentative, ambiguous language in his directives, reflecting either a lack of confidence in his plan or a misunderstanding of his opponent's posture -- perhaps both.
Burnside had reinforced Franklin's sector on the morning of battle to a strength of some 60,000 men. Franklin, a brilliant engineer but cautious combatant, placed the most literal and conservative interpretation on Burnside's ill-phrased instructions. Rather than clearly denote Franklin's attack as his main effort, Burnside ordered Franklin to attack the Confederate position with "a division at least" (a division numbers only 4,000-5,000 men). Lacking time to clarify, Franklin designated Major General George G. Meade's division -- just 4,500 troops -- to spearhead his attack.
Meade's men, Pennsylvanians all, moved out in the misty half-light about 8:30 a.m. and headed straight for Jackson's line, not quite one mile distant. Suddenly, artillery fire exploded to the left and rear of Meade's lines. Major John Pelham had valiantly moved two small guns into position along the Richmond Stage Road perpendicular to Meade's axis of march. The 24 year-old Alabamian ignored orders from Major General J.E.B. Stuart to disengage and continued to disrupt the Federal formations for almost an hour. General Lee, watching the action from Prospect Hill, remarked, "it is glorious to see such courage in one so young." When Pelham exhausted his ammunition and retired, Meade resumed his approach, Jackson patiently allowed the Federals to close to within 500 yards of the wooded elevation where a 14-gun battalion lay hidden in the trees. As the Pennsylvanians drew near to the Richmond, Fredericksburg, and Potomac Railroad north of Hamilton's Crossing, "Stonewall" unleashed his masked artillery. Confederate shells ripped gaping holes in Meade's ranks and the beleaguered Unionists sought protection behind wrinkles of ground in the open fields.
Union guns responded to Jackson's cannoneers. A full throated artillery duel raged for an hour, killing so many draft animals that the Southerners called their position "Dead Horse Hill." When one Union shot spectacularly exploded a Confederate ammunition wagon, the crouching Federal infantry let loose a spontaneous Yankee cheer. Meade, seizing the moment, ordered his men to fix bayonets and charge. Meade's soldiers focused on a triangular point of woods that jutted toward them across the railroad as the point of reference for their assault. When they reached these trees they learned, to their delight, that no Southerners defended them. In fact, Jackson had allowed a 600-yard gap to exist along his front and Meade's troops accidentally discovered it.
The Unionists pushed through the boggy forest and hit a brigade of South Carolinians, who at first mistook the attackers for retreating Confederates. Their commander, Brigadier General Maxcy Gregg, paid for this error with a fatal bullet through his spine. Meade's men rolled forward and gained the crest of the heights deep within Jackson's defenses.
Jackson, who had learned of the crisis in his front from an officer in Gregg's brigade, calmly directed his vast reserves to move forward and restore the line. The Southerners raised the "Rebel Yell" and slammed into the exhausted and outnumbered Pennsylvanians. "The action was close-handed and men fell like leaves in autumn," remembered one Federal. "It seems miraculous that any of us escaped at all."
Jackson's counterattack drove Meade out of the forest, across the railroad, and through the fields to the Richmond Stage Road. Union artillery eventually arrested the Confederate momentum. Except for a minor probe by a New Jersey brigade along the Lansdowne Road in the late afternoon and an aborted Confederate offensive at dusk, the fighting on the south end of the field was over.
Burnside waited anxiously at his headquarters on Stafford Heights for news of Franklin's offensive. According to the Union plan, the advance through Fredericksburg toward Marye's Heights would not commence until the Left Grand Division began rolling up Jackson's corps. By late morning, however, the despairing Federal commander discarded his already-suspect strategy and ordered Sumner's grand division to move to the attack.