Wearying at last of the inactivity Lincoln ordered General Burnside to take command of the Army of the Potomac, as McClellan's successor, and the new commander decided to move down the left bank of the Rappahannock and attempt a march upon Richmond by a short route.
Establishing his base of supplies at Acquia creek on the Potomac, only a few miles from Fredericksburg, with a railroad connection between, Burnside sat down on the north side of the Rappahannock, opposite Fredericksburg, the last of his columns reaching that point on the twentieth of November. Lee, moving upon a parallel line, reached Fredericksburg about the same time, and formed his lines to resist his enemy's contemplated advance.
Lee's army at that time numbered about 68,000 men, but before the battle it was swelled by reinforcements to nearly 80,000, and again reduced by detachments, to 68,000 or less. Burnside's force numbered about 120,000, with 147 guns, about twice Lee's strength in artillery.
Fredericksburg lies upon fairly level ground, immediately upon the southern bank of the Rappahannock, which at that point is not fordable at any season. In rear of the town and within cannon range, there is a line of bold hills beginning upon the river above the city and stretching in a curve around the town to the eastward where they gradually diminish in height and finally disappear.
Lee seized upon these hills and hurriedly fortified them, placing his artillery in effective positions and shielding his men with strong earthworks. Here he concentrated the greater part of his army under Longstreet on the left or west, and Jackson on the right or east, while D. H. Hill, with the remainder of the Confederate army was posted at Port Royal, twenty miles further down the river, eastward, to meet and repel any attempt that might be made to cross there and turn the flank of Lee's position.
This detachment of Hill with a strong force to a point so far away as to forbid his direct coöperation with the rest of the army during the battle, seriously diminished Lee's effective strength, but the advantage of position which he possessed and the advantage of fighting behind breastworks which his enemy must assail from the open, compensated him somewhat.
Burnside's first difficult task was to get his army across the river. This he could do only by the use of frail pontoon bridges of which he purposed to lay five – three in front of the city and two below. The pontoon trains were slow in arriving, and when they came it was for a time impossible to put the pontoons into position, owing to the destructive fire of the sleepless sharpshooters Lee had posted along the banks to interfere with the work. In consequence of this and other difficulties it was not until the tenth of December that a crossing was made which Burnside had confidently expected to make more than a fortnight earlier.
In the meanwhile Lee had busied himself night and day in strengthening his position in every possible way, and he was soon fully prepared for the contest.
Burnside's first assault was made about ten o'clock on the morning of December 13. It was made in two columns, striking simultaneously, the one against Lee's right and the other against his left. The assault upon his right was at first attended with a partial success, but Jackson hurried troops to the breach and quickly hurled the assailants back in confusion, pursuing them nearly to the river's bank where a heavy artillery fire checked his progress. The Federal assault on that part of the Confederate line was not renewed during the day.
From official reports and otherwise, it appears that Burnside at first intended to direct his main attack upon this right wing of Lee's army. The hills there were lower and far less defensible than were those on the Confederate left, and offered, certainly, a much more tempting opportunity to the Federal commander. It was without doubt the weakest point in Lee's line – the point which the Federals might have assailed with greatest hope of success or at least of inflicting the heaviest loss upon their foes. But, for some reason which has never been clearly explained, Burnside changed his plan of battle almost at the last moment, and directed his heaviest columns against Marye's Heights, the well-nigh impregnable stronghold of Lee's left wing. Here Lee had his batteries and a host of infantry strongly posted in formidable earthworks on top of the hills, in a position of great advantage.
For a body of troops to charge up Marye's Heights, bristling as they did with hostile and well served cannon, and defended by tens of thousands of veteran riflemen, was a task that might well have appalled even such sturdy fighters as composed the Army of the Potomac. But the matter was made more difficult by another peculiarity of the ground. Looked at from below, the hill seemed to present a smooth surface, ascending gently toward the works that defended it. But this appearance was deceptive. On the side of the hill well in advance of Lee's main line, and running athwart the Federal line of advance, there was a sunken road, faced with a stone wall, which formed as perfect a breastwork as any that an engineer could have constructed there. Into this sunken road Lee threw about two thousand riflemen, who lay there perfectly concealed from view and as well protected against adverse fire as men using rifles can be. Their orders were to withhold their fire until the enemy charging up the slope under a destructive cannonade from above, and thinking of the works at the top as the first obstacle to be encountered, should reach a point a score or so of yards in front of the sunken road, whence they could be swept away like dust before a housemaid's broom. It was as deadly a trap as could be imagined, and its concealment was perfect. Yet when the Federal general decided to make his main attack upon Lee's left, there was no course open to him but to take this doubly defended hill by assault or suffer fearful disaster, as he did, in a futile attempt to do so. For the nature of the ground on Lee's farther left rendered it impossible to turn his flank or try conclusions with him otherwise than by a direct charge upon Marye's Heights.
The first attack was made by French's division. It was already suffering terribly under the fire from the hilltop, when it came upon the sunken road and was instantly swept away by a hailstorm of bullets. Retiring, French left about one half of his men on the field, dead or wounded.
Hancock charged next with five thousand men and was driven back with a loss of two thousand or more.
The exact nature of the case was not even yet understood. The position in the sunken road was still masked to the Federal commanders. But French's and Hancock's attempts had conclusively shown that no courage, no determination, no heroism however high, could enable mortal men to carry that hill by assault. Nevertheless Burnside persisted where a wiser leader would either have withdrawn or have changed his plan of battle. He sent another, and another, and still another division into that fire of hell, only to see them instantly hurled back, shattered fragments of most gallant commands, beaten, broken and well-nigh destroyed by reason of a blundering obstinacy on the part of their commanding general.
Finally Hooker was ordered to make another attempt – the sixth of those futile and bloody charges. He pointed out to Burnside the uselessness of the effort and begged him to abandon without further needless sacrifice of gallant men's lives, an operation which had already been proved to be hopeless.
In a blind rage Burnside seemed unable to comprehend what his subordinates saw clearly enough. He insisted upon sending Hooker's command also into that slaughter pen. They rushed forward, – four thousand as brave fellows as ever fought in battle – and a few minutes later seventeen hundred of them lay stretched upon the field, their bodies riddled with Confederate bullets, while their comrades, unable to achieve the impossible, fell back as the remnants of the other divisions had done before.
The Confederate war furnished two conspicuous manifestations of supreme heroism on the part of large bodies of men – one upon one side, the other upon the other. Pickett's charge at Gettysburg was one of these. This series of six charges up Marye's Heights was the other.
When the sixth assault ended as its predecessors had done, the time had manifestly come to end the battle. A wiser commander would have ended it much earlier, indeed. Having lost 12,353 men in an ill-directed contest Burnside withdrew to the river bank, baffled and beaten beyond recovery.
The Army of the Potomac had won all the glory