Right from the opening scene one can view historical inaccuracies. First, there was no last great battle against the Germanic tribes the day before Marcus Aurelius' death. However, a great battle was fought late in the campaign in 179 C.E., yet Marcus Aurelius did not die until the year 180 C.E.#
This leads to another point of error in this film; Marcus Aurelius was not murdered by his son Commodus. It is believed that after two long winter campaigns along the Danube River Aurelius contracted the plague and died shortly after at the age of 59.
In fact, in actual history there is not even a motive for Commodus to assassinate his father and emperor. This event is completely false and was probably created to discredit Commodus and to prompt the viewers to hate him.
"Gladiator" also tells us that Marcus Aurelius had no confidence in his son, Commodus, and intended to return The Roman Empire to its roots as a republic, stating that "-there once was a dream that was Rome," which is again, completely fiction. The thought of any Roman Emperor denying his heir the throne is absurd.#
In truth Marcus Aurelius had named Commodus a joint ruler in 177 C.E. , making him the youngest joint ruler in Roman history up to that point. Then in 178 C.E. Commodus and Marcus Aurelius jointly commanded the war against Germania until Aurelius' death 180 C.E. This clearly demonstrates Aurelius' pure confidence in his son and disproves any notion that he would deny him the title of Emperor of Rome.
Also this opening sequence harbors some errors in Roman warfare. Firstly and probably most obvious is the use of catapults. There is no denying that the Roman army had the technology to create these great weapons, but the manor in which they are used in the film "Gladiator" is completely flawed.
The use of flame-hurling catapults does make for a fantastic visual and an intense opening sequence, but it is highly unrealistic. These weapons were used for siege warfare and would be highly cumbersome and immobile in the open fields of combat. The mobile armies of the barbarians would be too quick to properly aim at due to the complex measurements of angles and range required to effectively utilize such a catapult.#
Also the Roman army is seen using mechanical crossbows and cavalry in this great battle along the Danube. Like the catapult, the mechanical crossbow was commonly used in static siege warfare and would have been impractical in the open planes of battle. Also, the large units of cavalry seen charging through the wilderness is completely flawed. The Romans did have horses, but they were treasured beasts usually reserved for generals and other high-ranking officers in the military. It was highly uncommon to see a large Roman cavalry unit and even if the Romans did use cavalry more in their tactics it would not have been in the woods.
Large units of cavalry are most effective when formed in ranks, or lines. The lines then charge across the field of battle gaining speed and then trampling every man in their path. If one were to attempt such a glorious charge through the woods the line would become broken. The many trees would not allow for the straight path a field does and the cavalry would not be able to maintain the strong line in which they are most effective.
As for Commodus the movie somewhat misleads the viewers in many ways. The film's version of Commodus is portrayed as a single man in his mid twenties, when in reality Commodus was only 18 when he became Emperor of Rome after his father Marcus Aurelius died. Commodus was also married to Bruttia Crispina in the year 178...