That pic makes me shudder———but it was necessary.
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Twice in 25 years the world fought wars that killed a significant portion of the worlds population.
Why did we not have a third one around 1970? Because every time politicians started making the mistakes that would lead to a third world war, the images of those mushroom clouds was stuck in the back of their heads.
Those bombs killed the notion of “total war” between groups of nations dead. We haven't figured out how to live in peace with each other yet but we have come a long way from the era of massive world wide slaughter that existed from 1914 to 1945