On December 13, 1862, Union General Ambrose Burnside mounted a massive, yet futile frontal assault on Robert E. Lee's Confederate troops outside of Fredericksburg, Virginia. Wave after wave of Union troops hurled themselves at the Confederates, only to be mowed down in their tracks. In the end, the Federals suffered more than 13,000 casualties, making the Battle of Fredericksburg one of the worst defeats for the Union Army.