Notes

Battle of Fredericksburg:
No other battle could be compared to the gargantuan Battle of Fredericksburg, the largest fight of the entire Civil War with an astounding 172,504 combatants.
The Union met with their opponents in the streets of Fredericksburg, which would soon become the site of the Civil War's first urban battle. Under General Ambrose Burnside's command, they planned to use 60,000 men to obliterate the right flank of the South's army, which was led by General Robert Lee. Meanwhile, the rest of the Union, around 40,000 men, held another Confederate group in position at nearby Marye's Heights.
Then, the fighting began over a course of four long days, from December 11, 1862 to December 12. Though the Union's attack at Fredericksburg was successful in the beginning and showed promise of victory, they lacked reinforcements, and Stonewall Jackson's men powerfully counterattacked. These two factors led to heavy losses on both sides, yet with no strategic advancement in the end. At the same time, Burnside's army at Marye's Heights fared no better. In fact, they were greatly overwhelmed by the South despite having a far greater amount of men. The South's unpenetrable line of defense, devastating artillery and rifles, and height advantage was what led to the Union's downfall and much higher casualties, which, in fact, were 4,500 for the South, vastly smaller compared to 13,000 in the North.
Overall, Fredericksburg was an bloody, deadly, and humongous loss for the North... Needless to say, Burnside was removed from command several weeks after the battle.

Battle of Chancellorsville:
It was after the complete failure of Union General Ambrose Burnside at the Battle of Fredericksburg that President Lincoln decided to replace him with someone else- a man named Joseph Hooker. General Hooker's tactics drastically renovated the Union army's condition. With more strength than ever, they were able to outflank Lee's party and arrive near Chancellorsville on April 30th, 1863. Little did they know, however, that the vast and unpopulated wilderness surrounding Chancellorsville would become a key point in their future demise.
General Lee needed a strategy. First He collaborated with his uncomparably brilliant lieutenant, the renowned Stonewall Jackson, to hatch what would be their last and greatest plan together.
The battle finally ended on May 6th, six days later.