User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-170.235.245.52-20130520190059/@comment-24339098-20130522202447

It was never stated that the cause of WW1 was demigods (though it is likely). WW2 was the children of Hades vs the children of Zeus and Poseidon. The American Civil War (which is the bloodiest war in American history) was a war between the Greeks and Romans (as were other civil wars).