Answer:
Mongolian invaders traveled extremely quickly and were very highly trained and disciplined.
Step-by-step explanation:
Usually an army is worried about being overwhelmed by the sheer number of combatants they face. However, a highly mobile force like Genghis Khan’s can also cause great fear in an enemy because they have the ability to travel quickly and to strike without warning. This fact combined with the advanced skills of Mongolian warriors produced a lethal effect, and cities often surrendered without a fight when Genghis Khan showed up.