These are the American Civil War: Brothers vs. Brothers 3.6 Open Beta manual install files
Detailed install info here: Twcenter.net
Current build of 3.6 Open Beta supports Warpath map based ACW campaign only.
However, users who don't own Warpath can still play the custom battles and a limited RTI campaign with all the new units!
Also, remember this is a BETA of 3.6, so several features aren't working and the installation is not smooth. Unfortunately there is also a likely campaign crash present, but you can use older campaign files for a more stable build.
For all additional info, go to the forum: Twcenter.net
Reduce the chance of battle crashes by turning down your graphics settings and disabling Steam overlay.