The Dutch documentarist Joris Ivens' anti-fascist cinema of the late 1930s coincided with his invention of the solidarity documentary. His Chinese film The 400 Million (1938) is analyzed as a prototype of the subgenre in respect to its development, production and reception. The film is seen in the light of problems inherent in the classical-sound documentary aesthetics as it embraced anti-fascist politics, and in particular intercultural issues related to frontline film-making in a China united by a precarious Guomindang-Communist coalition.