Couldn't this easily be solved with a WW3 prediction market? Why try to find proxies for such an event when one could speculate on the outcome directly? It's simply a more efficient market.
Deep OTM calls on VIX (ETF ticker $UVXY) would be something similar to that. If WW3 happens, VIX will skyrocket.
Furthest expiry available as of today for $UVXY options is Jan 16, 2026.
Although you could try to collect your dues at the rubbles of the clearing house
By definition, a prediction market doesn't work if one side is betting on the prediction market ceasing to exist.