Bots make their return in Call of Duty: WWII and can be played offline on all game modes, including War. The maximum number of bots that can be added is 17 (War mode however is capped at 11 bots).
You need an Internet connection to initially download content. Once Modern Warfare Remastered has been downloaded, you do not need to be connected to the Internet to play/launch the Single Player Campaign or play Multiplayer locally. Will Call of Duty: Modern Warfare Remastered come as a separate disc?