What about the "mongol storm from the east" you must have attended religious school.
They stormed the East and the west and conquered China many parts of the Middle East.
They were so effective because they were horsemen, the composite bow (which was not effective in the land of the ice and snow where I come from). They were hard men and disciplined too. I do believe if you gave hitler 9 million men like me we'd all be speaking german. It can do a lot.