Although none of us want a world war to happen, because war never brings peace. But yes, your idea is right, during the war, the value of the country's fiat currency will definitely decrease and can that currency disappear if the country is destroyed. Yes, but if you have a good amount of Bitcoin. Then if you save your life, you can definitely do something. But I am worried that if there is a world war, will the servers of big giant companies be destroyed?