By early 1863, Union soldiers with the Army of the Potomac had not been paid for 6 months and supplies were thin. Some 200 men were deserting every day and by January one-quarter of the men were AWOL. Gen. Ambrose Burnside, the new Union commander, wanted to take Fredericksburg but delays in getting the pontoon boats to cross the Rappahannock river allowed Lee to amass 75,000 men. The Union army was blown away and 9,000 men were killed. (imdb)