These kind of WWIII scenarios always feel a bit speculative to me - it really depends on how this war will be fought: will it be traditional warfare (in the worst case even including nukes)? Will it be an escalation of what we are seeing right now (i.e. terrorism in western countries -> western countries retaliating with combat in other countries). Or will it be purely cyber warfare?

On one hand, I can understand the notion that Bitcoin seems like a good alternative for when this kind of Doomsday scenario happends. But keep in mind: a global war of unseen sizes would likely also destroy considerable parts of the developed worlds electrictiy and network infrastructure. What good is my BTC, if no digital services are available anymore to facilitate payment with? Thats why my tendency is to say: if you want to be a Doomsday Prepper, prepare entirely for an offline, no-electricit life. So buy yourself tradeable goods (food, medicine, gasoline etc) that will be valuable even if all IT infrastructure is disabled.