Factual error: The movie is set in 1944, when there were only 48 states, yet we see many American flags with 50 stars, then 48, then back to 50 throughout the film.
Factual error: Near the end of the film, Nicolas Cage is looking at the envelope of a letter sent by the Second Class Petty Officer that helped him pass his hearing exam. On the envelope, her Rating (a job in the Navy) is written as HM (Hospital Corpsman). During that point in history, those jobs were called PH (Pharmacists Mate). There were no HM's in the Navy then. The envelope should have read PH2 not HM2.
Factual error: Just an observation here: Do you ever notice how the wound/kill radius on a lot of the heavy artillery explosions is like 1-2 feet. In one explosion (usually against the Japanese), the artillery does massive damage, i.e. takes out an entire bunker, but another round will land almost right next to guy and it does virtually nothing. I also wonder where all the shrapnel is, almost all the explosions in this movie create a lot of dirt or a lot of fire, but no shrapnel or its effects.
Factual error: Throughout the movie, most of the artillery and grenade explosions produce massive fireballs, as though each one hit a fuel depot. In reality, explosions of most artillery shells produce a lot of dirt, dust and smoke but very little flame unless they produce secondary explosions of gas tanks, etc. In Windtalkers, even explosions that go off in empty ground produce prodigious fireballs.
Factual error: Late in the film, Nicolas Cage throws a grenade to kill the Japanese who have captured Roger Willie. The resulting explosion is a prolonged pyrotechnic plume with petroleum flames bursting out of the ground. WWII grenades didn't produce flames of any kind, and they still don't.
Factual error: When the Christian Slater character is introducing himself to the Nick Cage character while running on the beach, he mentions that his nickname is "Ox" because he comes from Oxnard, CA. He then explains that Oxnard is "just north of Hollywood a ways". But look at a map - Oxnard is practically due WEST of Hollywood, not North. Someone from Oxnard would know that.
Factual error: When Ox and Whitehorse are being over run at one point Ox points his .45 at the Japanese and repeatedly pulls the trigger (you can here the click , click ,click sound of the hammer hitting an empty chamber.) This is a mistake because in order to do this the .45 would have to be a double action pistol its not you must manually cock it to get it to fire the first round (after that it cocks itself hence the name Auto Loader).
Factual error: Throughout the film, Joe Enders is wearing an M1 Helmet. But his helmet looks like a non-WW2 type and possibly Vietnam era. From the side of the helmet, it is a higher cut along the sides. This is a usual indicator to the era of the helmet, as WW2 M1 helmets are lower along the ears for better protection.