Burnside knew he had to rescue his badly tarnished reputation by another assault on Fredericksburg.  On January 20th he began moving his army back toward Fredericksburg, only to be greeted by rain, and more rain.  The roads turned to a sea of mud and his army bogged down, exhausted from four days of futile effort to move forward.  The endeavor was another disaster – though only to the army's morale and Burnside's personal reputation.  Three days later Lincoln replaced Burnside with "Fighting Joe" Hooker as commander of the Army of the Potomac.

Meanwhile considerable trouble was being stirred up by another group of opponents to the war, largely from among the anti-War Democrats in the North (especially Ohio) – who eventually drew the label "Copperheads."  Under the leadership of Clement Vallandigham, they opposed the draft, opposed "King Lincoln," opposed the Emancipation Proclamation and called for an immediate peace with the Confederates (which would have left the issue of Southern slavery untouched).  Republicans accused the Copperheads of treason, and in May of 1863 Vallandigham was arrested by a military tribunal for encouraging Americans to take up arms against the Union.

Much controversy followed his arrest, so Lincoln decided that rather than try him for treason, Vallandigham was to be banished to the Confederacy.  Vallandigham eventually made his way to Canada, and proceeded from there to be nominated as a Democratic Party candidate for Ohio governor.  He subsequently lost the election, but deepened the division among the people of Ohio over the questions of the war and of slavery.¹

However, with the continuing advance of the Union armies against the Confederacy, support for the Copperheads would eventually fade away. But they would be a serious problem for Lincoln until things finally began to improve.

¹While still in Canada Vallandigham attempted to set up a Northwest Confederacy of Ohio, Kentucky, Indiana, and Illinois as an ally of the Southern Confederacy.  But nothing came of the plans.  He slipped back into the U.S. in order to be able to attend the 1864 Democratic National Convention (Lincoln decided simply to ignore him) hoping to be the party's presidential nominee.  But that honor was to go to the ambitious General McClellan instead.

Meanwhile back East in Virginia, Union General Hooker had spent the winter months of early 1863 rebuilding the demoralized Northern Army of the Potomac. In the spring, he set out in the direction of Fredericksburg, but swung to the west of the town to draw Lee's army away from it.   At a crossroads clearing known as Chancellorsville, elements of the two armies met.

But despite having more than twice the number of troops as Lee, at this point Hooker strangely took a defensive position, though he sent part of his men to try to sweep in behind Lee.   Lee then attacked Hooker and for two days both armies fought fiercely, until Hooker disengaged and retreated back across the Rappahannock River, humiliated in his inability to defeat an army less than half the size of his.  Lincoln would soon replace him with yet another general, George Meade.

But the loss was great on both sides.   The Union lost 17,000 soldiers, and the Confederates nearly 13,000 soldiers.   But the Confederates also lost Jackson when a Confederate guard mistakenly shot Jackson while the latter was out late at night studying the land in preparation for the next day's action.  Jackson died on the 10th of May, a huge loss to the South.

After Chancellorsville, Lee understood that his best strategy would be once again to take the war into the North and conduct a bold strike against the Northern army, which in turn would likely force Lincoln to have to give in to the rising voices in the North demanding immediate peace with the South.

When Meade got his new orders to take command of the Union Army of the Potomac, Lee already had a number of his troops in southern Pennsylvania, with the Confederate cavalry leader Jeb Stuart raiding the countryside.  It looked as if Lee intended to grab the Pennsylvania capital, Harrisburg, so Meade gathered his forces and headed northwest from Maryland to intercept him.  On June 30th, at the small Lutheran seminary town of Gettysburg, forward elements of the two armies met.

For the next three days the two armies fought each other, the Union armies holding defensively the upper grounds and the Confederate armies attempting to dislodge or even surround the well-entrenched Union position.  This time the immense boldness of Lee did not suffice to carry the day, despite the enormous effort Lee applied to the task of overrunning the Union position.  Even a massive frontal assault across one mile of open field produced merely huge Confederate losses.  Finally, on July 4th, Lee ordered the retreat of his army – back toward Virginia.

Tragically, Meade did nothing to pursue the retreating enemy.  He and his troops were exhausted.  But so were Lee's. Once again, like the generals before him, Meade could not think past the issue of the battle at hand and understand that he had a war, not just a battle, to win.  By letting Lee escape back to Virginia, he had let slip by the opportunity to end the war then and there. Lincoln was pleased with Meade's victory, but was upset that Meade had missed what to Lincoln was an obvious opportunity to crush Lee's army and end the war.

Yet it was still a grand disaster for the South – and Lee recognized immediately that he had gambled the lives of his men foolishly.  He lost 28,000 of his 70,000 troops. But it had been costly for the North as well.  Meade had lost 23,000 of his army of 90,000.  Nonetheless, it was Lee, not Meade, who had been broken by this action.  Lee would never be able or willing again to try an assault on the North. Henceforth, the war would involve the South trying to protect itself from invading Northern armies. Gettysburg (and Vicksburg) then marked the turning point of the War, although at the time this was not widely understood in the North.

The action now moved to the center of the North-South line of battle, along the Tennessee River in Southeastern Tennessee.  Union General William S. Rosecrans's Army of the Cumberland had been pushing General Braxton Bragg's Confederate troops south through Tennessee, and having reached Chattanooga in August they were ready to now push into Georgia.  In the meantime, Rosecrans had sent Burnside to Knoxville (where there was considerable pro-Union sentiment) to secure that city for the North.  It had all been fairly easy.  But that was about to change.

In his push south into Georgia, Rosecrans did not get very far before running into a deep forest along the Chickamauga Creek where (unknown to Rosecrans) Bragg's forces had been reinforced by Confederate General James Longstreet's troops. Although operating blindly in the dense forest, the Confederates found a gap in the Union lines, split the Union forces in two, and then turned hard on one of the two Union groups. It was a Union disaster.  But the other half, under General George Thomas (a Virginian who had stayed loyal to the Union), held off the Confederates long enough to let what was left of the Union Army retreat back to Chattanooga.²

It had been a devastating battle for the Union ... but also for the Confederates. The Confederates suffered 21,000 casualties compared to 16,000 Union casualties. Thus the Confederate "victory" at Chickamauga had come at a huge price that the South could ill-afford.

The situation in Chattanooga for the Union army grew desperate, as it was now surrounded by well-positioned Confederate troops who had cut off the Union army's line of supplies (including food). In October, Lincoln had put the entire central and western command under Grant, who in turn replaced Rosecrans with Thomas as the new commander of the Army of the Cumberland.  And Grant pushed strongly forward to make sure that supplies and troops (Hooker's troops from the East and the troops of General William Tecumseh Sherman from the West) would make it past the Confederate blockade.  By late November the Union army was finally resupplied and ready to fight.

The biggest challenge was the huge Lookout Mountain from which the Confederates could still threaten Chattanooga and hamper the movement of goods and troops in and out of the town.  That had to be taken – although it was well defended by Confederate troops atop a 500-foot-high cliff.  In fact, it was so well defended that Bragg decided to send Longstreet and his troops off to retake Knoxville, considerably reducing the size of the Confederate army in position at Chattanooga.

Grant's plan was to send Hooker's troops around one side of the mountain and Sherman's troops around the other side, with Thomas's troops to hit the mountain straight on, mostly as a diversionary action until Hooker's and Sherman's troops could get into position.  But Thomas's troops, once they got going, refused to halt at the foot of the mountain, and began to climb wildly straight up its heights, terrorizing the Confederates, who could hardly believe what they were seeing. In the end, the Confederates scrambled back up the mountain and then over the other side, and did not stop running until they were well out of range.  The Union army had thus broken Bragg's position, and now a humiliated Bragg was forced to retreat south.

In the meantime, Union General Burnside had been able to hold off Longstreet's Confederates at Knoxville, and with Sherman now able to come to Burnside's assistance, Longstreet was forced to break off his efforts to retake Knoxville.

At this point the Union army settled in at Chattanooga for the winter – in preparation for the next spring's offensive against central Georgia, the very heart of the Confederacy.

²Thomas would be called the "Rock of Chickamauga" for his role in saving Rosecrans's army.