Early on, he helped introduce German experimental film in Japan, and was instrumental in getting Teinosuke Kinugasa's masterpiece A Page of Madness screened in Tokyo.
[3] When Prokino was effectively eliminated by police oppression under the Peace Preservation Law, Iwasaki continued his critical activities, becoming involved in the Yuibutsuron Kenkyūkai with such thinkers as Jun Tosaka, but was eventually arrested in 1940, in part for his opposition to the Film Law, which authorized increased government control of the film industry.
[5] After his release, he worked for a time at the Tokyo office of the Manchukuo Film Association thanks to the help of Kan'ichi Negishi.
He joined Nihon Eigasha (Nichiei), primarily a documentary film company, and helped produce two important, but ill-fated documentaries: The Effects of the Atomic Bomb on Hiroshima and Nagasaki, which was confiscated by Occupation authorities,[6][7] and The Japanese Tragedy, directed by Fumio Kamei, which was banned for its critical depiction of Emperor Hirohito.
[8] While continuing to work as a film critic from the 1950s on, including pursuing a vigorous debate on the nature of cinematic realism with Taihei Imamura, Iwasaki helped produce some of the independent films made by Tadashi Imai and Satsuo Yamamoto after many left-wingers were expelled from the major studios in the Red Purge.