The most common cause of war is the failure to correctly predict its outcome

 

This stems from the mistakes of overestimation of self-ability, underestimation of adversaries, and unexpected actions of third parties/nations.

Would Hitler attack Poland if he saw June 1945 Germany and his own body?

Would have European countries started WW1 (WW2 is continuation of WW1) if they saw the same 1945?

If China saw the lost century, it would spend more money on the military like Great Britain, and then the British aggression and the opium wars likely wouldn’t have happened.