WWII and LOTR..Compare/Contrast

[Rumil]

Two particular points which I noticed regarding LoTR and WWII were;-

Tolkien states that he was 'stuck' with the story on reaching Balin's tomb during the dark days of 1941. I imagine that the war must have understandably depressed and agitated JRRT, especially with his son serving abroad, and that he lost the appetite to continue his tale. If I remember, he started again later in 1942, where the situation had improved somewhat in that the USA and USSR were now our allies and Hitler looked to be stoppable. I wonder if it is possible (HoME readers?) to relate the events in the real war to the War of the Rings in respect of the time each occurred / was written? If the Nazis had won perhaps LoTR would have ended with the victory of Sauron and now be banned as anti-Fascist allegory!

I've always been reminded of the atomic bomb explosion when the Fall of Barad-Dur is described, and Tolkien, in the passage above, seems to me to imply a link between 'the ring' and 'the bomb'. Could anyone say when the Fall of Barad-Dur was written (or foreshadowed!), before or after Hiroshima?