This film pioneered the use of jump cutting to and from a flashback, and of very brief flashbacks to suggest obtrusive memories.
Eiji Okada (playing Lui) did not know any French and was coached in pronouncing each syllable and memorized that order.
This started life as a documentary about the nuclear bomb drop on Hiroshima until Alain Resnais decided to include fictional elements.
The film utilizes footage originally from the movie Hiroshima (1953) without ascribing credit.
The scene in the Hiroshima Peace Memorial Museum early in the film includes several scenes from the 1953 Japanese film Hiroshima (1953), which starred Japanese actor Eiji Okada, who also plays the leading role in this movie. For obvious reasons, no footage that featured Okada from the earlier Japanese production was included.