Single player RPG for WW2?
Men of War: Assault Squad 2. Currently ~£4 on Steam and is fantastic. A lot of micromanaging if that's your thing, but no need to be that on top of things in single player. Plenty of single planpl missions to get through and then there's always the Steam Workshop for more content.
Company of Heroes 2 is also a great game, but the single player lacks a bit or content, multiplayer / comp stomping is where it excels!