WaW adds 100 new Units, 73 new Buildings, 55 new Technologies, 18 new National Wonders, and 1 new Era to the game. The goal is to expand the gaming experience “vertically not horizontally” – meaning, it expands content by adding more to the types of things that are already in the game (Technologies, Units, Buildings, Wonders), but not add new things or drastically change the way any of these existing systems behave. WAW is not a “replacement game.” It is trying very hard NOT to be. The goal is to provide a significant expansion to existing game systems, but not to completely re-work the way the game normally plays. WaW seeks to change this by greatly expanding the gaming possibilities of the latter part of the game. What should be the most interesting part of the game is often the quickest part of the game. There is little time to experience what should be the most varied and interesting aspects of civilization building and military conquest.
Usually when I play Civ V, I'm often taken aback at how quickly the last few Eras fly by. The World at War (WAW) is a comprehensive modification to Civ V (BNW) that adds a much deeper playing experience to the second half of the game.