Toshirô Mifune entertained the cast and crew throughout the entire production with his refined culinary skills, bringing over a supply of Japanese meats, watercress, seaweed, and other ingredients. He would also exchange recipes for French and Italian dishes, including spaghetti.
This movie made Charles Bronson a huge star in Japan. Around this time Bronson also did an ad for a Japanese cologne, for which he earned $100,000 for just four days work.
The Japanese ambassador was played by Tetsu Nakamura, a Japanese actor known for his excellent command of the English language. It is believed that he coached the non-English speaking Toshirô Mifune for the English dialog required.
The busy schedules of Alain Delon and Capucine meant that they flew back to France and Switzerland, respectively for weekends and were helicoptered back to the location each Monday.
John Huston considered this, Rio Vermelho (1948), and No Tempo das Diligências (1939) to be among the three best westerns ever made.