War would see an increase in bitcoins price but a natural disaster? I'm not sure. It depends how many places it affects since if it's just a small country or a few islands it wouldn't affect the price at all even if the people there had to spend all of their bitcoins.
natural disaster such as earthquake, tsunami, and the other big disaster will affect internet connection, and if the disaster is in the country which citizen are mostly bitcoin users, I think the price will decrease because of course demands will decrease too and spending bitcoin will decrease either.