The lesson was writ plain by Thucydides centuries before Christ was born. Democracy satisfies best the human thirst for freedom; yet, being undisciplined, turbulent, and luxury-seeking, it falls time and again to austere single-minded despotism.
In the World War II setting of War and Remembrance, obviously the "single minded despotism" was Nazism, and secondarily Soviet Communism and Japanese militarism.
Now, it's radical Islam. We were very very lucky to escape those other single-minded despotisms. We're sixty years further down the decline of our culture; I wonder if we'll be lucky -- or blessed -- again.