what physical feature might have prevented the Mongols from conquering In Dia ?? (HELP THIS IS DUE TONIGHT !!)

by improved communication.

we pointed them north: recollections of a cowpuncher by e.c. “teddy blue” abbott tells us of the history of nomad cowboys in north america. as the   frontiers began moving west, trails of cowboys of the 1870s and ’80s drove herds of cattle from texas to the northern ranges and railheads, and then rode back south to do it again. they gradually pushed   native americans out of their lands, until in 1889 the   government transferred white   colonists the indian land.

where is the map if i see it i can give you the answer