In the Bible, the first sin was not war, but it carried the seeds of war. Eve wanted to do it her way, and to hell with the consequences.
Indeed. To hell with the consequences. No surprise that the second generation in the Book of Genesis went to war. Two brothers, and in church too, or at least in a situation parallel to church: The Lord accepted Abel's offering and rejected Cain's. Cain got mad, and got no sympathy to boot, even though he was a modern man who believed that God is supposed to be glad with whatever we are glad to give him. God doesn't even get it that he is in the wrong! He seems to think Cain is in the wrong! The Lord said to Cain, "Why are you angry, and why has your countenance fallen? 7If you do well, will you not be accepted?
Who does God think he is, anyway? By refusing Cain's offering, he lost the right to speak to Cain. So Cain takes care of it himself. He gets rid of his problem by getting rid of his brother.
It doesn't work though. It almost never does. The trouble with "to hell with the consequences" is that they don't go to hell right away. They hang around. The blood of Abel cries from the ground. Cain cannot say, "Can't be helped," because there it is. The consequences aren't swallowed up in hell. God says to Abel, "Your brother's blood cries to me from the ground."
It still cries, because Cain rejected God's warning: And if you do not do well, sin is lurking at the door; its desire is for you, but you must master it."
God does not accuse Cain of sin. Cain had not done well, but he had not yet sinned. His failure to do well had opened him to temptation. Sin was lurking at the door, but it had not yet entered; It was Cain's to master. Instead, he let it master him. He opened the door to it and killed his brother, thus providing a primal archetype for human history.
I had a second major in history as an undergraduate. In those days over fifty years ago at a small liberal arts college, history was taught as collective memory; for it to work, academic discipline was rigorously applied to correct faulty memories and their flawed interpretations.
History is not so much what we remember as it is the viewpoint we assume as we remember: "Okay, somebody screwed up big time, but it wasn't us, we have the witnesses to prove it, and we have the lawyers (or scholars, or politicians, or "experts") to demolish your witnesses. Not going to take our word for it? If you want to fight about it, we'll fight you."
And that is why, little children, our systems of justice, defense, education, and governance so often fail to produce justice for the innocent, defense for the helpless, learning for the uninformed, or governance that pursues these goals.