In explaining the importance of a successful bond drive, the treasury representative says that the fuel dumps are empty and "our Arab friends only take bullion." At the time of World War II, America was essentially self sufficient in oil production and not dependent on Arab oil. While oil was discovered in some Arab countries before the war, it was not extensively developed until after the war.
When Ira Hayes leaves on the train, the modern rubber warning material (used to warn blind pedestrians that they are approaching the edge) are visible, although painted gray. These are modern (post 1990) innovations.
When Ira, Rene, and Doc are getting off the train there is a band playing for them, one of the alto saxophone players is using a leather ligature on his mouthpiece, a post WWII invention. During WWII they would have used metal ligatures.
Petty officer Badley's white uniform is post war. You can see two slits for the pockets. Pre-war dress whites had such pockets, but with a blue yoke and cuffs. Postwar dress white uniforms have them as well. During WWII, a simple patch pocket of the Undress White uniform was used, dress whites being discontinued for the duration.
When the train arrives at the station, the Locomotive is an EMD F-3 or later model. The F-3 was first built in 1946. Only the original FT model was available during the war and it only had a single number board, below the headlights, whereas the one used in the movie had the larger number boards on either side of the nose which was characteristic of the class from the F-3 on.
During the montage of newspapers being opened to show the raising of the flag one has the person removing a rubber band. The modern rubber band, as we know them, ans as shown in that scene, was not patented until March 1945. Paperboys delivering newspapers to houses commonly folded the page-turning side (right side) into the fold side (left side) in order to throw them.
When Lt Gen Smith is on the phone just prior to the invasion, he references "scrambled eggs" upon their chest. Scrambled eggs is a term for the gold oak leaf branches field grade officers wear on their covers (hats). Fruit salad is a term used to describe the ribbons worn above the left breast pocket on the service and dress uniforms.
There are several scenes in the movie where there are continuity problems with the helmet chin straps. For example, near the beginning of the movie, when Doc and Iggy are in the shell crater from which Iggy disappears, Doc's chin strap is tight, then loose. Similarly, when Ira Hayes comes out of his tent at the training camp, his chin strap is fastened, then unfastened. There are other examples.
When the 2nd platoon arrives late at the beach, Sgt. Strank yells something like "Get your bag" at a trooper still on the swim tank, but outside the frame. Few seconds later, Strank gives a hand sign to the tank driver to pull back. By then, no further trooper, let the one in question was seen jumping off the tank.
Daylight pictures of "Soldier Field" (the flag raisers learn they will be climbing a paper mache hill) are actually filmed at the Rose Bowl (note the trees above the bowl which are the characteristic live oaks that surround the Rose Bowl). Of course, the "Soldier Field" stadium shots at night are computer graphics aided as the signature columns are no longer visible from inside the bowl since the recent massive renovation of this 80 year old stadium.
When Ira Hayes goes to visit Ed Block (Harlon Block's father) at his farm near Weslaco, Texas you see mountains in the background. The Block farm was in the lower Rio Grande Valley of deep South Texas, which is quite flat. (Despite its name, it isn't a valley at all but the delta of the Rio Grande). The nearest mountains are in northern Mexico, over 100 miles to the south.
During the ending credit roll, an actual photo taken during the heroes meeting with President Truman shows sailor John H. Bradley using a pair of crutches. In the film's re-creation of the event however, Bradley is shown without using or needing the aid of crutches.
During the initial bombardment of Iwo Jima by the U.S. Naval
Fleet, the distinctive shape of several Iowa Class battleships is shown (their bows had a unique curvature when seen in profile). One of these ships is shown taking a direct hit from Japanese batteries. Three Iowa-Class battleships were present at Iwo Jima and did perform shore bombardment duties, but none was hit as depicted in the film.
Chandler Johnson, the commander of the 2nd Battalion 28th Marines (played by Robert Patrick), was a lieutenant colonel (silver oak leaf rank insignia) but is shown wearing the eagles of a full colonel.
During the bond tour, Corpsman 'Doc' Bradley wears no ribbons on his Navy uniform. He should have been wearing, as a minimum, the same service ribbons as Hayes and Gagnon. In addition, Bradley also won the Navy Cross and the Purple Heart on Iwo Jima, and should also be wearing those ribbons if they were awarded before the bond tour began.
During the flag-raising, Mike Strank is shown wearing a soft cap. In the real-life film clip of the flag-raising, shot by Sergeant Bill Genaust, all six of the flag raisers are wearing helmets. In one or two frames at the very beginning of the real-life clip, light, shadow and the camouflage pattern make Strank's helmet look like it might be a soft cap, but he is clearly wearing a helmet in the remaining frames where his head is visible.
In the train scene were Keyes Beech offers a toast, John "Doc" Bradley refers to Beech as "sir." Beech, wearing the rank of Gunnery Sergeant, would on occasion be called "Sir.", in Boot Camp everyone of Higher rank was referred to as "Sir."
In the "Bond Tour" scenes involving old-time microphones, only once is the microphone positioned correctly. When the "Andrews Sisters" vocal trio sings and the men later speak, the black-and-silver RCA 77 ribbon microphones are positioned backwards. They should have been rotated 180 degrees, so that the microphones' fronts and tops would tilt slightly away from the singers/speakers. The same is true for a later scene with one of the men speaking at a lectern with a large gray Altec microphone - it, too, is positioned backwards.
After planting the flag, the unit is attacked by a couple of Japanese while waiting on the mountain top. The standing soldier's bayonet can been seen flexing back and forth as he moves his gun. Clearly it's a black rubber prop bayonet.