Les envahisseurs attaquent

This film is considered the last entry in the Golden Age of Toho's kaiju films, and meant to be the last film of the Godzilla series. However, it was successful enough that it was decided to continue the series, albeit as part of a film campaign called the Toho Champion Festival, a seasonal matinee that specifically targeted children. This meant that subsequent films would have to reduced their budgets and staff since the Godzilla films were just too expensive to continue making in their original manner. For example, this film and the ones prior had two or more large groups of crew members that divided the work on the character drama and special effects sequences. Case in point: cinematographer Taiichi Kankura shot the live action character drama directed by Ishirô Honda, while different cinematographers, Yôichi Manoda and Sokei Tomioka, shot the monster sequences directed by Sadamasa Arikawa. Subsequent films reduced this to a singular crew that had to manage all of those aspects at once.

When the news reporter in the film announces that Baragon is destroying Paris, France, it is actually Gorosaurus. The Baragon suit was loaned out to Tsubaraya Productions for use on one of their TV series and was not returned in time for filming.

In Toho's international version of the film, its English-language credits list special effects director Sadamasa Arikawa as "Sanemasa Arikawa."

A Toho Video documentary released in the 1980s contained several unused and deleted scenes from this film. The majority of this footage consists of alternate takes of finished scenes, such as the raids on Moscow and Paris by Rodan and Gorosaurus, respectively. Toho also filmed much more footage of the United Nations' defense of Tokyo from the monsters, including a number of scenes of missile launchers being deployed from the roofs of skyscrapers. The most notable unused scene in this feature has Godzilla thrashing Manda against several Tokyo buildings. According to Haruo Nakajima, this was an impromptu act at the end of a take. This was likely removed from the finished film as both monsters were under the Kilaaks' control and should not have been fighting each other.

Edited into Objectif Terre, mission Apocalypse (1972)