To make it look like Robert De Niro and Natascha McElhone were actually driving during the car chase, right hand drive cars were used, with the passenger side made up to mirror the real controls. The actors then mimicked the stunt drivers movements.
The figure skater, Natacha Kirilova, is announced as having won two Olympic and three world championships. She's played by Katarina Witt, winner of two Olympic and four world championships in figure skating.
The script originally called for Sam chasing Gregor in the arena to stop at the railing. However, at shooting, the stuntmen accidentally toppled over the railing, falling hard on the stone surface below. Director John Frankenheimer decided to leave the accident in the film.
The reference to the "man in the wheelchair" is referencing the book "The Bourne Identity" (1980) by Robert Ludlum; not the 2002 movie. The Man In The Wheelchair was M. Chernak, a mercenary broker that Jason Bourne killed.
David Mamet worked on the film as a script doctor. He significantly re-wrote the script, making major changes to character and dialogue from J.D. Zeik's original. There was a dispute between the studio, the director and the WGA over the credit, with MGM and the WGA insisting that Zeik be given story credit and billing over Mamet. They wouldn't back down and so Mamet asked that his name either be removed or placed under a pseudonym. The credits of the film now read as "Story by J.D. Zeik. Screenplay by J.D. Zeik and Richard Wiesz".
In Japan nowadays, 'Ronin' not only means a 'masterless Samurai', it also refers to students who haven't been accepted to a particular university and spend a year studying to take the entrance exam again the very next year.
In a 2008 readers poll conducted by CAR magazine, 4 cars featured in this movie merited ranks in the magazine's "Top 40 Coolest Movie Cars" issue: Audi S8 (9th), Citroën XM & Peugeot 605 (24th) and BMW 535i (29th). Other featured vehicles included, Peugeot 406, Citroën Xantia, and a (rare) Mercedes-Benz 450SEL 6.9.
During one of the car chase sequences where Gregor (Stellan Skarsgård) is dictating directions to Sam (Robert De Niro) from a computer terminal, Avid film editing software - the software used to edit the film - is visible on the screen.
Almost all scenes were shot on location with the exception of two scenes. The opening scene used a set with the couple walking past the camera as the matching shot between location and set. The other one was the sequence between Sam and Vincent in the car right after the former was wounded. It was shot in green screen.
Sean Bean claims to be an S.A.S. veteran based in Hereford. In Bravo Two Zero (1999), Bean plays an S.A.S sergeant and mentions that Hereford is his home base. Hereford (on the England/Wales border) is the site of the S.A.S. regimental headquarters, known as Stirling Lines.
The 'fish in the barrel' scene was nearly scrapped when filmmakers encountered inconsistent weather over the period of 5 days. They instead settled for wetting the road and the car to give the impression that the place just rained. Also, even though there was a French by-law forbidding gunfire during photography during early-hours in the morning, the authorities gave special exception for the filmmakers.
Director John Frankenheimer actually owned a similar brown Mercedes that was used in the second car chase scene. Although the script did not mentioned which car Vincent and Sam would use to chase the convoy, he suggested having the Mercedes being used in the movie.
This was filmed in Super 35 despite "Filmed in Panavision" being listed in the end credits. This has confused some people, however Panavision is a company which makes cameras and lenses and many films are made with Panavision equipment which are not not necessarily "Panavision" in the sense of "shot with an anamorphic lens made by Panavision".
Two of the actors later play fathers of main characters in the "Pirates of the Caribbean" franchise: Jonathan Pryce who plays Governor Swan, Elizabeth's father and Stellan Skarsgård who plays Will Turner's father.
At the end of the chase in which the case is taken by the team and then stolen by Gregor, a French SWAT team arrives. The first SWAT man leaps out of the van armed with the very impressive Franchi SPAS-12 riot shotgun. Moments later another SWAT man is shown armed with the extremely rare Franchi SPAS-15 shotgun, the almost unknown successor to the SPAS-12. The SPAS-15 uses a detachable box magazine, shown clearly. Ronin may be the only major movie appearance of the SPAS-15.
The trivia items below may give away important plot points.
The contents of the silver briefcase is never revealed, making the briefcase a good example of a modern 'MacGuffin', a plot device often employed by 'Alfred Hitchcock'. A MacGuffin is an object that serves to drive the plot forward without having any importance in itself. As such, the object or its purpose often remain unidentified.
In the part where De Niro is shot and has the bullet removed, he says the bullet was Teflon coated and that is why it penetrated the vest. Such bullets were sold in the USA until they acquired the reputation of "cop killer bullets" and were taken off the market.
The conversation between Sam and Jean-Pierre explains the history of the 47 Japanese samurais who became 'Ronin', masterless warriors betrayed by a feudal lord, who later took revenge against him. This plot was later loosely depicted in 47 Ronin (2013).
Like the cut near the start of the movie that transitions from on-location to the set of the café, there is a similar cut at 1:04:59 that transitions between locations as Seamus is approaching Larry in the parked car. The passerby between the camera and Seamus obscures the transition. The first part of the scene takes place where Rue de la Bastille meets the Amphitheatre, the second part is in a small courtyard, with an Oleander, just up some steps, west of the Arenes d'Arles. At 1:04:59 Seamus is on the Rue de la Calade and and at 1:05:01 he is in the small parking court. This is the same court where Diedre enters the car to find Larry has been killed by Seamus, and Sam and Vincent arrive in time to see the car drive away, looking down at Larry's body. When the camera cuts back to Sam and Vincent looking down, they are actually back on Rue de la Calade.