From their website:
Well, after lots of game report, lots of reading, research, frantic figure painting and darned good fun, Terrible Sharp Sword is now available. It wasn’t long after the publication of Sharp Practice that we began to get people asking about an American Civil War version, indeed Chris Stoesen produced a number of scenarios in the 2009 Summer Special that really got me started with my ACW collection and since then it’s been non-stop painting to add to that.
So, what can you expect from Terrible Sharp Sword. Two things, I hope. Firstly the game is fun; we all spend a lot of time working hard in these tough old times, so naturally it’s important that what spare time we get for gaming in an enjoyable experience. Secondly, I hope that you’ll find a system that allows you to get an appreciation and understanding of warfare in the American Civil War, and some of the tactical problems that were faced historically. Whilst the system is firmly anchored to the base of Sharp Practice the game does differ in some substantial ways in order to attempt to create the feel of the war between the States, and I thought it would be a good idea to outline some of these here.
Check out their blog post for more details on the new features and changes in this ruleset.