Answer:
Reports of the Mongol attacks terrified Europe. The Mongols increased their empire using swift and decisive attacks with an armed and disciplined cavalry. They wiped out the populations of some entire towns that resisted, as was their usual policy, depopulating some regions and confiscating the crops and livestock from others. This type of total warfare spread panic even among Europeans not directly affected by the Mongol onslaught and sent refugees fleeing westward.
Perhaps even more importantly, the Mongol conquest of central Asia and Eastern Europe allowed a deadly disease—the bubonic plague—to travel from its home range in western China and Mongolia to Europe along newly-restored trade routes.
Step-by-step explanation: