At 51m 12s there are 4 ranks of soldiers clearly visible facing the center. As the camera tracks backwards following Napolean there are only the center two ranks visible, the outer ranks have vanished.
During the Battle of Waterloo, the infantry present in the lines change between shots.
In the credits scene at the end of the movie, Louis-Napoleon (Emperor Napoleon III) is said to have died in 1871, whereas he in fact died 1873 in Chislehurst, England.
According to the plot Talleyrand is warning Louis XVIII of Napoleon advancing to Paris. In reality, Talleyrand was at that time at the Congress of Vienna and not in Paris.
Talleyrand is advising the king in France while Napoleon is advancing to Paris. History records that Talleyrand was in Vienna during Napoleon's return.
During the battle of Waterloo, one of the British flags is upside down. The other one is the right way up.
During Marshal Ney's first charge, the British and French cannons are shown to be less than 200 yards apart. Cannons typically engage at ranges much longer than that because one side would be able to annihilate the other without opposition if it sets up too close to the other.
When the Imperial Guard is dispatched, they begin to move without an order being issued.
During the Battle of Waterloo, many of the soldiers on both sides lack cap badges.