As soon as Doug and Tony arrive in the 13th century, Doug gets his right pant leg deeply stained with dirt. However the stain disappears during the ensuing fight scene with the Mongols.
Doug Phillips implies that the black powder that Polo is taking back to Europe lacks nitre (aka potassium nitrate); however, surviving Chinese records from the ninth century show that existing formulae (two centuries before Polo's time) contained from one-quarter to one-half nitrate content. Gunpowder without nitrate would not, in fact, be sufficiently explosive to make even the firecrackers Polo describes.
Anne MacGregor reports that Sarit was the "...only daughter of Kublai Khan who married a dark-haired, fair-skinned stranger from a faraway place..."; the notion that she is the only daughter is repeated by Marco Polo. Kublai Khan was known to have had at least three daughters; the only recorded marriage was his daughter Khutugh Beki, who married a Korean crown prince and became empress of Goryeo, a Korean kingdom allied with the Mongol rulers of China.
The plumes on the Europeans' helmets may have been good for ceremonial display, but on soldiers operating from a defensive position all they do is provide targets.
Gunpowder must be tightly confined in order to explode; The containers used were too fragile.
Tony is out cold and laying on the ground while Doug converses with Marco Polo. As Doug begins to pick up his friend you can see Tony assisting him even though he should still be knocked out.
The helmets and other costumes shown in the battle scenes do not match up with those in the close-up scenes, undoubtedly due to the use of Taras Bulba (1962) stock footage for the large-scale fighting. Similar mismatches occur between the distant and close-up views of the fort.
When the soldiers are loading equipment into the tunnel, their shadows and the shadow of the equipment are clearly visible on the backdrop used to make the tunnel look "infinite".
Batu died in 1255. Kublai Khan started his reign in 1260. Kublai and Batu would not be opponents.
By 1287, the Chinese had been aware of the existence of gunpowder for about 500 years, and had been using explosive grenades in warfare for at least a century. Its properties as a weapon would have been familiar to the Mongols, who were rulers of China during the Yuan (Mongol) Dynasty, which lasted from 1271 to 1368.
When Doug and Tony are first discovered by the Mongols, in the large grassy clearing, there are obvious modern tire tracks everywhere.
Doug Phillips calls Marco Polo "...the first European to explore the Orient..." On Polo's famous trip east, he accompanied his father and uncle, who had already been to China and met Kublai Khan before him. The difference, of course, is that Marco dictated a memoir of his trip while his elders did not.
When the European fighters ambush Tony and Doug's Mongol pursuers, the Mongol warriors hold their shields away from their bodies - not an effective stance for a trained fighter.