In 2012, Mount & Blade: Warband – Napoleonic Wars developer Flying Squirrel Entertainment announced that it was on a new project based on the US Civil War called Battle Cry of Freedom. It sounded like an extremely ambitious undertaking, with large 5x5 km maps, historically accurate weapons and uniforms, fully destructible environments, and support for 500-player (!) online battles—all of which may help explain why it took nearly a decade for it to finally appear on Steam.
Note that it isn't actually on sale yet, nor does it even have a release date: The listing is there strictly so followers can "wishlist the game and follow the page to be notified whenever there is new info available." But the fact that it's there at all is noteworthy in its own right. Flying Squirrel has been posting fairly regular developer blogs on its website since 2012, but the rollout of the Steam page is the game's biggest and most public step forward since it was announced.
Battle Cry of Freedom still sounds much like it did in 2012, with multiple weapon and ammunition types, realistic projectile physics, and an array of roles for players ranging from basic infantry to engineer, surgeon, and even musician: You can become a fifer, drummer, or bugler and play "historically accurate tunes," if that's how you want to roll. It's not meant to be a detailed military simulation, however: The FAQ describes it as "a mix between Mount & Blade and the Total War series," saying that it aims to combine "a realistic and skill-based combat system with the huge size and tactics of epic warfare."
The promised 500-player battles are out, though: Instead, the Steam page says that up to 300 people will be able to go head-to-head "in a completely destructible and realistic Civil War combat environment," which will still make for some pretty beefy conflicts.
Battle Cry of Freedom is currently expected to be out sometime in 2022, and while you wait for that to (hopefully) happen, you can find out more about the game at fsegames.eu.