moral defensive. Disappointed by McClellan's failure to destroy Lee's army, Lincoln named Ambrose Burnside the commander of the Army of the Potomac. Burnside ordered an attack across the Rappahannock River at Fredericksburg, Virginia. Delays in bridging the river allowed Lee's army ample time to organize strong defenses, and the Union frontal assault on December 13, 1862, was a disaster. There were 12,600 Union casualties to 5,000 Confederate, making the engagement one of the most one-sided battles in the Civil War. After this victory, Lee reportedly said, "It is well that war is so terrible, else we should grow too fond of it." At Fredericksburg, according to historian Michael Fellman, Lee had completely entered into the "spirit of war, where destructiveness took on its own beauty." The bitter Union defeat at Fredericksburg prompted President Lincoln to appoint Joseph Hooker as the next commander of the Army of the Potomac. In May 1863, Hooker maneuvered to attack Lee's army by crossing the Rapahannock further upriver and positioning himself at the Chancellorsville crossroads. Doing this could give him an opportunity to strike Lee in the rear, but the Confederate General barely managed to pivot his forces in time to face an attack. Hooker's command was nearly twice the size of Lee's but he nonetheless was beaten after Lee performed a daring movement that broke all terms of conventional warfare: dividing his army. Lee sent Stonewall Jackson's corps to attack Hooker's exposed flank, on the opposite side of the battlefield. The decisive victory that followed came with a price. Among the heavy casualties was Jackson, his finest corps commander, accidentally fired on by his own troops. Even though he scored another impressive victory over an enemy army much larger than his own, Lee felt unsatisfied by the fact that he had made little territorial gains up to that point. Things were going poorly for the Confederacy in the West, and Lee started to grow restless; he devised a plan to once again invade the North, for similar reasons to before: relieve Virginia and its citizens of the weariness of battle, and potentially march on the Federal Capital and force terms of peace. Battle of Gettysburg Critical decisions came in May–June 1863, after Lee's smashing victory at the Battle of Chancellorsville. The western front was crumbling, as multiple uncoordinated Confederate armies were unable to handle General Ulysses S. Grant's campaign against Vicksburg. The top military