Question

What ultimately led to Burnside losing the Battle of Fredericksburg?

Answer 1

The general answer would be that he failed to coordinate his attacks. He attacked on the right, where Jackson was, and actually broke through for a little while but was pushed back by Jubal Early. Then he attacked on the right where the entrenched Longstreet was--the famous stone wall at Marye's Heights and Sunken Road--and was completely slaughtered. Completely. And he never attacked the middle, where some have argued Lee was weakest. So Number One is piecemeal attacks.

Another reason is simply the difficulty of frontal assaults against fortified positions. Some historian argue (this is hindsight of course) that mere common sense should have told Burnsides how hopeless a frontal assault would be on Lee's position. Lee also had interior lines that made it easy for him to shift troops to where the fighting was hottest. However, recall that the roles were switched at Gettysburg, and Lee the great tactician also ordered a disastrous frontal assault. It was not unusual military practice. And it should be said for Burnsides that he was under tremendous political pressure to do something--attack Lee. So politics at home played a role too.

If you want to go even farther back, you can cite the delay of the pontoon bridges that allowed Lee to fortify so strongly before Burnsides could get there in the first place. And there is always the human factor: Burnsides was a reluctant commander; he didn't want command, didn't think he was capable. In this instance he was correct. Lee was surprised and disappointed at how soon Burnsides retreated (on the advice of his senior corps commanders, it should be said). It seemed like a half-hearted attempt after all.