In one scene, combat veteran Sgt. Stryker (John Wayne) instructs bumbling recruit Pvt. Choynski (Hal Baylor) on the correct way to march and hold a rifle. In real life Baylor was an ex-Marine who fought in the battles of Saipan and Tinian in WW II; Wayne had never served in the military.
The three men who were part of the flag raising (made famous by the photograph Joe Rosenthal had taken) and survived the battle for Iwo Jima, appear in the movie. Rene A. Gagnon, Ira H. Hayes and John H. Bradley are seen with with John Wayne as he instructs them to hoist the flag. (Wayne gives the folded flag to Gagnon). The flag used to recreate the incident is the actual flag that was raised on Mount Suribachi on February 23, 1945. It was loaned to the movie by the US Marine Corps Museum in Quantico, Virginia.
Following the success of the movie, John Wayne was invited to place his footprints in cement outside Grauman's Chinese Theater. As part of the event, actual black sand from Iwo Jima was flown to Hollywood and mixed into the cement in which The Duke left his footprints and "fist print".
Kirk Douglas was originally cast as Sergeant Stryker.
John Wayne almost turned the film down at first, since at 42 he was rather old for the part and because he felt the American public had had enough of war films.