more surprised by a crossing immediately in our front than any other part of the river. ... I'm convinced that a large force of the enemy is now concentrated at Port Royal, its left resting on Fredericksburg, which we hope to turn." In addition to his numerical advantage in troop strength, Burnside also had the advantage of knowing his army could not be attacked effectively. On the other side of the Rappahannock, 220 artillery pieces had been located on the ridge known as Stafford Heights to prevent Lee's army from mounting any major counterattacks. [ 15 ] Model of a portion of the pontoon bridge built for the film Gods and Generals , displayed at the Fredericksburg and Spotsylvania National Military Park Pontoon bridges at Franklin's Crossing Union engineers began to assemble six pontoon bridges before dawn on December 11, two just north of the town center, a third on the southern end of town, and three farther south, near the confluence of the Rappahannock and Deep Run. The engineers constructing the bridge directly across from city came under punishing fire from Confederate sharpshooters , primarily from the Mississippi brigade of Brig. Gen. William Barksdale , in command of the town defenses. Union artillery attempted to dislodge the sharpshooters, but their positions in the cellars of houses rendered the fire from 150 guns mostly ineffective. Eventually Burnside's artillery commander, Brig. Gen. Henry J. Hunt , convinced him to send infantry landing parties over in the pontoon boats to secure a