At first, my chapter had no history - just the 18th North Carolina in the dark waiting for the threat to materialize around the bend in the road.
Could it be that the first chapter is just too long. If I just did the missing of Jackson and the orders to Hill to cut the Yankees off at the US Ford... then it might be a faster easier read.
What do you think of putting the terrain and the history leading up to Chancellorsville into a prologue. That way it is optional? If you don't know the history...read it. If you do, do what I do to prologues... pass them by. Introductions too except they usually are the most important part of the book.
"putting the terrain etc. leading up to Chancellorsville..."
That would work if you personalized it somehow. For instance --- whatever time of year it is, there could be farm work going on. I.e. 'the farm wagon loaded with field corn lumbered through the hilly terrain, and the farmer spilled his load at a ..." some particular site with a bluff or whatever is important. Even better, 'Farmer Witherspoon's last load of corn spilled repeatedly on the hilly terrain..."
Or if it's not hilly, then his wagon moves easily over the flat ground...
Then you get your description through a person.
“It is spring and the air is warm but contains the promise of the desert. Soon, the skies will remain redunant blue with no clouds to shield the rays of the sun. Moisture in any form, dew or rain, will be a forgotten memory by May, well, not unless you count the sweat on my brow. Then Tel Aviv will be awashed in moisture!”
Quit before you rot your underwear.