A king that wanted to make war had to tax his people. In democracies inflating the currency is a more politically palatable way to raise money. Bitcoin is harder to confiscate and impossible to inflate. If I don't support your war I memorize my seed, and cross the border looking like a poor refugee when in reality I'm a billionaire.

Doesn't mean that war will become a thing of the past, just that it will require a much higher level of social cohesion and support.