I stumbled across this list of genocides and the raw numbers of everything were surprising – seemingly far more clustered in Europe and more in the 20th century than one would expect.
An interesting notion arose from this Hacker News comment thread about the life and legacy of John von Neumann – specifically the contrast between decision making under certainty (i.e. hindsight) vs decision making under probability. The topic in question was pre-emptive war with the Soviet Union in the late 1940s and early 1950s. After thinking about it for a while I came to the horrible realization that it wasn’t the worst idea in the world. bit actually something of a close call.
I’m left being even more grateful for the presidency of Dwight Eisenhower. The 20th century was a scary time.