Five Came Back (2017): A documentary adaptation of Mark Harris' book (which has been deemed a film, and thus worthy of inclusion on this site, even though its primary distribution method is in an episodic form on Netflix; oh, O.J.: Made in America, what hast thou wrought?), which has some advantages over its literary cousin in that, when telling the story of a group of filmmakers, it's useful to be able to illustrate one's points with actual footage of the films being discussed.
Each of the five directors covered (Frank Capra, John Ford, John Huston, George Stevens, and William Wyler) has been paired with a contemporary director to comment on their work (respectively, Guillermo del Toro, Paul Greengrass, Francis Ford Coppola, Lawrence Kasdan, and Steven Spielberg), which for cinephiles provides a lot of the most interesting moments -- I'd never have pegged del Toro as such a passionate admirer of Capra, for instance.
I was a budding history nerd as a kid, and my parents bought me a VHS set of Capra's propaganda films that they found in a local department store at the time. They made for fascinating viewing, and some of the images (particularly the cartoons) stuck with me through the years. It's interesting to get a look at what the other directors were doing, and the range of experiences they captured. By far the heaviest material concerns Stevens' time in service, which culminated in his documenting the atrocities at Dachau and effectively ended his career as a director of comedies (the laughs wouldn't come anymore).
There are times where it feels like some peripheral figures, such as a black screenwriter involved in the production of a film about black soldiers serving in the army (it's noted that a poll of Harlem residents taken at the start of hostilities found that about half thought their lives wouldn't be much different under the Nazis, which occasioned the project), could have been developed a bit more. We also see explored the racist elements of the anti-Japanese propaganda, and, contrary to what one might expect, it's people in the government trying to tone it down (one must credit the wisdom of General MacArthur in insisting it not be shown).
The final segment also offers some really fascinating insights into some of the directors' immediate postwar work. The Best Years of Our Lives' relevance is fairly obvious, but the insights offered in respect of It's A Wonderful Life and Capra's investing his own personal struggles into George Bailey will change how you look at the film (one of my favourites).