Among those who saw the film on its US release was a young Clint Eastwood. Richard Schickel writes in his 1996 biography of Eastwood: "Treasured among these films and stars [that Clint Eastwood saw while growing up] is one slightly more exotic title, 'Forty Thousand Horsemen'. The story of an Australian cavalry brigade that fought in Palestine in World War I, it starred Chips Rafferty, was made in 1940 and entered the world market a couple of years later. Its dialogue contained a few mild, but in those days shocking, cuss words. Clint remembers going to it with his family and, when the first 'hell' or 'damn' was heard, being aware of respectable citizens leaving the theater. The Eastwoods soon followed, but 'I snuck back later, because I wanted to see the whole movie; it had a lot of action--horses, and lancers and what have you'."
As the cavalry charge scene would necessitate falling horses, Charles Chauvel was afraid that the horses used in the film would be injured from the traditional stunt means of using trip wires. He contacted the RSPCA about filming the scene in the most humane manner possible. RSPCA co-operation with the stunt crew saw to it that no horse was injured in their stunt work.
Director Charles Chauvel's uncle, Gen. Sir Harry Chauvel, had commanded the New Zealand and Australian desert corps in Palestine in WW I. However, he never mentions his uncle's part in the battles, because he didn't want the film to be seen as a family tribute.
When the film was presented to the Australian censor, Creswell O'Reilly, the scenes of the falling horses looked so realistic that he insisted they be cut from the film. Charles Chauvel personally invited the Minister for Customs to see the film and decide for himself. The film was passed uncut and broke all Australian box office records to that date.