I had started asking myself this question quite a while ago but couldn’t reach a conclusion. First of all, different people may have different definitions of “who started a war first”. I have two kids, whenever they were caught fighting each other, I had a hard time figuring out who started it. Because it’s a typical positive feedback loop: it has always started with something small but since no one is willing to take the necessary steps to cool down the situation, it turns into a real fight soon. My standard is whoever started the physical first got punished because that behavior changed the nature of the conflict: some disagreements that were resolvable by negotiation/discussion/compromise suddenly out of control and turned ugly until a stronger power (parents) step in and put both backs to the negotiation table. 

Let’s use the same concept here. I’ll describe whoever started the action with the intention not to negotiate but to suppress the other party as the war starter. And I’ll list the examples I have collected so far and I’ll be love to collect exception cases.