If you are following the time line of 1862 with me, after the disaster at Antietam, good came for the South in December, at the Battle of Fredericksburg. In November, Lincoln had replaced McClellan with General Burnside, But Burnside didn't last long because he tried to cross a "little stream" and the Confederates were up on "the top of the hill", waiting for him.
To those of you who know your Confederate Battles, the "stream" was the Rappahannock River, and "the top of the hill" was called Marye's Heights, a strongly fortified ridge just west of the city of Fredericksburg. It was one of the most one-sided battles of the Civil War, with Union casualties twice that of the Confederates.
Those sharpshooters in grey just mowed down Burnside's men as all day long, the Yankees tried to cross the river.It was like "shooting fish in a barrel". I have been there too, and seen it from the heights looking down. By the way, the word "sideburns" come from "Burnside" as he had very heavy ones.