Strange Victory, by E. R. May

The story of German victory over France in 1940 and how it came as a surprise in front of apparent material Allied superiority. The book describes the political developments in France, Great Britain and Germany running up to September 1939 before turning to a comparison of their armies. The comparison is first on a material level, where the difference is not great and often in favour of the Allies and especially France, then on the organizational level, especially decision-making and "intelligence", where the failings of the Allies are deep. Finally it gives a detailed narration of the "Battle of France" and how a rather risky German plan eventually routed the French army, partly through luck, but, as Pasteur said, luck favors the prepared mind, not those who are "always a little behind time and slow of mind", as one French general was described by his superiors at the time.