I don't know much about history, but isn't this supposed to be about the very beginning of war, when things were still very uncertain?
Anyway, I've got gripe with the presentation itself. The way Bruce described it before the album came out ("he was a flawed character, but overcame his flaws..."), I thought it would be something about facing his personal demons, but instead we got what looks to me like a collection of superlatives and hollow phrases (which I already had too much of in my own country, so maybe for that reason I'm extra irritated that Bruce would go down such a path).
The instrumentation, atmosphere and musical texture of the song is great, and conveys the title "Darkest Hour" much better than the lyrics themselves