- California Doubling: Yugoslavia doubled for Nazi-occupied France.
- Contractual Obligation Project: Clint Eastwood signed to do the film mainly because his friend and favorite director, Don Siegel, was set to direct it. However, Siegel ran into post-production problems while finishing up Two Mules for Sister Sara and had to withdraw from the project. Brian G. Hutton was then signed to direct. Eastwood, who had already signed a contract to do the film, couldn't pull out.
- Deleted Scenes: The studio cut 20 minutes from the film. Deleted material includes:
- Oddball and his crew pack up to go across the lines to meet up with Kelly and others while local village girls are running around half naked.
- The platoon encounters a group of German soldiers and naked girls swimming in a pool.
- While they wait for Oddball in the barn at night, Kelly and Big Joe talk about their disillusionment with the war and why Kelly was made as a scapegoat for the attack that resulted in his demotion. Another scene was deleted from this part where the platoon decides they do not want to continue with the mission, and Gutowski threatens Kelly at gunpoint, but Big Joe and Crapgame side with Kelly.
- General Colt is in bed with some women when he gets a call that Kelly and others have broken through the enemy lines.
- During the attack on the town, production designer Jon Barry had a cameo as a British airman hiding from the Germans.
- One promotional still shows Kelly finding a wounded German soldier among the ruined houses during the final town attack.
- Kelly, Oddball and Big Joe discuss tactics while standing on an abandoned Tiger tank before the scene where they negotiate with the German tank commander.
- When Kelly and platoon drive off at the end, a bunch of soldiers yell at them that they are headed in the wrong direction.
- Executive Meddling: According to Clint Eastwood, MGM, against both his wishes and those of director Brian G. Hutton, re-edited the film to remove some character-driven scenes and a more obvious anti-war message. This was also responsible for the addition of "Burning Bridges" as the title song, rather than the original theme composed by Lalo Schifrin.
- What Could Have Been: The film was going to have a female role, but prior to filming, it was cut from the script. Ingrid Pitt, who was cast in the role, (and had been in Where Eagles Dare with Clint Eastwood the prior year) revealed that she was "virtually climbing on board the plane bound for Yugoslavia when word came through that my part had been cut."
- Working Title: The Warriors and Kelly's Warriors.
- During the filming in Yugoslavia in July 1969, Neil Armstrong became the first man to walk on the moon.
- This film is an obvious favorite of the makers of Girls und Panzer, including one character calling herself "Sargent Oddball" as a hasty alias, and one team of girls watching the movie for inspiration the night before the national finals. Said team invokes "Operation Kelly's Heroes" in said final battle.
Trivia / Kelly's Heroes