Now there's at least one sword and sandal epic centered on Attila and his supposed efforts to marry the sister of one of the last Roman emperors, Valentinian III ruler of the Western Empire until he was assassinated in 455. The USA network also also did a miniseries about ten years ago. Not bad. I wonder if Valentinian was really THAT much of an idiot. Attila was Hun. His armies included members of his own tribes, soldiers from other tribes, but I'm pretty damn sure there weren't any Mongols.
The Mongols began their conquests under Genghis Khan in the early 1200's,reaching it's greatest extent by the end of the century, then fracturing into four separate khanates. The Mongols were known for their brutally ruthless battle tactics. If your city surrendered you lived. If your rulers insisted on resisting and the Mongols laid siege to the city, when the city fell you died. Brutal, Incredibly brutal. They ravaged Poland and Hungary. Destroyed the Russian cities of Kiev, Vladimir and Moscow.
It took me less than five minutes of strenuous research on Google to double check my facts. If I could do it so could who ever wrote the script. And I'll just leave it at that.