From a Wall Street Journal review by Adam Kuper of book by Christopher Blattman titled “Why We Fight: The Roots of War and the Paths to Peace”:

On July 30, 1932, exactly 6 months before Hitler became chancellor of Germany, Albert Einstein sent a despairing letter to Sigmund Freud. “Dear Professor Freud,” Einstein wrote. “Is there any way of delivering mankind from the menace of war? It is common knowledge that, with the advance of modern science, this issue has come to mean a matter of life and death for civilisation as we know it.”