In old western historiography, up to like 40-50 years ago Mongols were often portrayed as wild savages, “scourge of god” etc. Socialist historiography was more neutral on them (like Lev Gumilev or Stanisław Kałużyński). Recently westerners did close to a 180 on them though, as part of the historical revision trend going for at least 3 decades (most of that trend is actually not that bad, for example new critical look on ancient roman sources, still a lot worse than marxist view but a lot better than uncritically quoting Suetonius for example). From the top of my head read anything by John Man or Justin Marozzi.