The subject of the majority of the movie is the period between noon on August 14, 1945, and noon on August 15, 1945, when Emperor Hirohito's decision to surrender to the Allies in World War II was broadcast to the Japanese people, and the attempted coup d'état to prevent that from happening.

[2] The film featured dozens of Toho's contracted male actors as well as independent and borrowed stars like Chishū Ryū, Yūnosuke Itō, and Kōji Mitsui.

[5] Shinobu Hashimoto won the Kinema Junpo Award for best screenplay.

[6] The film was re-released theatrically in Japan on November 21, 1982 as part of Toho's 50th anniversary.

[7] A remake of Japan's Longest Day, identically titled in Japanese but released in English under the title The Emperor in August, was issued in 2015 by Shochiku, directed by Masato Harada.