Based on the same historical events as depicted in The Dreyfus Case (1931), The Life of Emile Zola (1937), I Accuse! (1958), Prisoner of Honor (1991) and An Officer and a Spy (2019).
The speech Emile Zola is doing in the cafe when talking to the young people who support Esterhazy is based on his "Open Letter to the Youth", that was released on the 14th December 1897.
While receiving one of the top billings in the movie Heinrich George (playing writer Emile Zola) only appears first after 50 minutes within the movie.