In my opinion, a world war is literally the worst thing that can happen to humanity, with or without bitcoin.

Wars happen because countries can't pay up their debts, so they "pay up" this way. (Again, in my opinion, no misunderstandings)
In a war, the fiat loses its value. I had a discussion with a friend about what could happen to bitcoin in a war. He said that it will surely collapse. I am not so sure about it.

Although, think about it for a while. In a world war, the last thing someone has is access to the internet. Would bitcoins lose their value?