Factual error: The strong current of the river the main character falls into carries him to a considerable waterfall. There is not, nor has there ever been, a river of that kind in the Ecoust front line area, let alone a waterfall. Anyone who has any insight into the geography of the region will tell you it is flat as can be. The largest body of water, the Yzer, gently meanders and flows into the Channel, even during really rainy times.
Suggested correction: I do not believe that either Ecoust or Croisilles Wood is in Flanders. Both are behind the old German lines at the Somme. That said, there are no bodies of water in that area.
Ecoust and Croissilles are in department Pas-De-Calais in the French Flanders, together with the Belgian flanders they are called Flanders Fields. It is indeed a flat area.
Also, the message in ink delivered is legible, despite having been submerged in water. And don't get me started about the attack from ridiculous trenches and not a barbed wire in sight.
It's not. Even French Flanders is further north. But, even though there are some high points in the area, like Vimy Ridge that rises to about 500 feet above the surrounding plains, the slopes are quite gentle. And, as you say, wouldn't allow for the kind of drop seen in the movie.
There is a watercourse that goes through Croisilles... But it's basically a ditch.
Factual error: During the battle at the Marshalls-Gilberts, the movie shows mountainous terrain. The real Marshalls and Gilberts are atolls with very little terrain.
Factual error: The American soldier on the balcony is waving a 50 star flag. (01:30:06)
Factual error: At presentation of the Medal of Honor, the US Air Force Secretary reads the citation that states William H. Pitsenbarger was an Airman First Class (E-3 with 2 stripes) but in the battle scenes William H. Pitsenbarger is wearing the insignia of a 'Buck' Sergeant (E-4 with 3 stripes). (00:14:29 - 01:43:55)
Factual error: The main character Lewis Morgan is supposed to be a British Army Colonel, but his uniform is wrong. Full Colonels are classed as Staff Officers and wear a Red band around their Service Dress Cap, a Staff Officers Cap Badge (a lion on top of a crown) and Red collar patches. It's also unlikely that a person would have reached the rank of Colonel without any medals which would be worn on Service Dress. (01:20:00 - 01:22:00)
Factual error: At one stage a soldier calls the Air Force Ground Liaison Officer "Captain", when his real rank is Group Captain, a much higher rank.
Suggested correction: 'Captain' (not to be confused with army rank 'captain' equivalent to a flight Lieutenant) is short and informal for the rank of 'group captain'.