It's unfortunate that the video seemed purposely ambiguous. It seems to say that you have to expand your territory by fighting other players. Yet I have seen other people on the forums absolutely convinced that you only lose resources and not territory in warefare.
So what is the real answer? Is there a home city that can't be lost and you expand into losable territory? How does the whole system work?
Perhaps we could get a directly no BS response or FAQ update with how the PVP works? That will make or break this game for a lot of people I would assume.