Ha! I figured it out. I guess a career in software development helped out. Here's what is happening:
When you launch a game, it starts out with the modal showing the 5 theaters to choose from.
Then when you choose a theater, you have a long scrolling list of battles. As you select one or the other ...

Eh.. I can't register because it wants an answer to this question:

"Who was the original publisher?"
This question is a means of preventing automated form submissions by spambots.

Ok thanks

Hi.. got this John Tillers Civil War recently and really enjoy it. Running Win 11 on an alienware laptop. I can save and open "btl" files for Antietam, Bull Run, Chickamauga, but it errors out on Shiloh & Gettysburg. Any idea why? I installed the update.