“…Kids, there is going to be one hell of a big-ass war between two competing evil axes, and the government that you all are paying taxes to is the leader of one of those evil axes. I’m sorry, but this Lee Greenwood Pollyanna shit has got to stop. That country no longer exists….”
Remember, too, that a casus belli does not have to be (and often is not) legitimate.
“Plausible” in significant part will suffice in most cases.