Interesting. Pre-World War II Poland was governed by Jozef Pilsudski, a figure very similar to Hitler in terms of autocratic control, and not necessarily a nice guy. But Roberts seems to omit the Battle of Britain (1940) in the question of who was first to bomb protected cities. Also, Hitler refrained from using poison gas out of personal repugnance, having been a poison gas victim on the front in World War I. According to my father, who lived through the times preceding World War II, the culpability of FDR in the runup to Pearl Harbor was understood by many.

It is also helpful to read the history of the "other side" during the same periods.