1929.jpgThere are moments when tectonic plates shift and history changes course.

Sometimes those shifts are barely perceptible — the Treaty of Versailles that ended World War One but also bred German resentment and the rise of Nazism; the Yalta conference that helped create the United Nations as a guardian of peace but also led to the Iron Curtain that divided Europe for nearly half a century; and the Great Depression (arguably the greatest catastrophe of the 20th century, says Martin Wolf).