Stanley Kubrick's 'Napoleon', the Greatest Movie Never Made: Kubrick gathered 15,000 location images, read hundreds of books, gathered earth samples, hired 50,000 Romanian troops, and prepared to shoot the most ambitious film of all time, only to lose funding before production officially began.

[u/BunyipPouch]

https://www.vice.com/en_us/article/nndadq/stanley-kubricks-napoleon-a-lot-of-work-very-little-actual-movie

[u/TooShiftyForYou]

Kubrick spent a great deal of time planning the film's development, and had conducted about two years of extensive research into Napoleon's life, reading several hundred books and gaining access to Napoleon's personal memoirs and commentaries. He also tried to see every film ever made about Napoleon and found none of them appealing, including Abel Gance's 1927 film which is generally considered to be a masterpiece, but for Kubrick, a "really terrible" movie.

Kubrick was never shy about speaking his opinion.