From the publisher’s website:
Battle Above the Clouds is the 8th game in the award-winning Great Campaigns of the American Civil War (GCACW) series. This is the first game covering a western theater campaign and will serve as the core area for a series of maps covering the entire corridor from Nashville, Tennessee to Atlanta, Georgia. The game includes both the Chickamauga campaign of August/September, 1863 and the Chattanooga campaign of October/November of the same year.
Battle Above the Clouds uses the same GCACW Standard Basic Game Rules that were first published in MMP’s Skirmisher magazine and Grant Takes Command. The game scale remains unchanged for the western campaigns, although two new terrain types (hills and ridges) have been added to properly represent the rugged terrain that dominates the Chattanooga area.