Option 2: If World War III looks more like Cold War II(a bunch of proxy wars and hostility between the Western World and Russia-China) Bitcoin adoption would continue and we might see a higher Bitcoin price(or BTC would simply preserve value, while fiat currencies are declining).
It looks the most likely scenario, as global leaders won't wish to implode themselves in a nuclear attack side by side with their enemies, or to suffer the consequences of a nuclear catastrophe.
Therefore, Bitcoin can be used to fund the war. It's a powerful currency to send between allied countries to supply financially each other without using traditional banking system.
For countries which don't want to involve directly on the conflict, Bitcoin is the way to go in order to help allies indirectly or in secret...