Answer:
When there are smaller units, the country can send those out instead of the larger ones.
Explanation:
This can both save on military resources for less-critical fights in wars as well as forcing the enemy to let down their guard.
It was primarily "<span>d. the vulnerability to invaders from the north", since the Mongol territory was rapidly expanding--making the Mongol warriors all the more powerful. </span>
The answer to that is the Native Americans.
