A typically Mongol military campaign involved being in the saddle for months to years at a stretch. Women simply are not made to do that. Our women, theirs, anybody's.
I've been riding horses a long time...
Never bothered me...
I of course,have not had occasion to ride them into battle...
Or for months/years at a time...
I can pull a 40 lb bow....
It hangs proudly over my fireplace...
This woman is Acadian/Native American....
Maybe I am missing your point...
What's the issue?
Historical?
Ms.B
The Americans (hey, that's us) have this one-dollar coin that bears the picture of a pregnant teenage girl, Sacajawea, who accompanied our other cousins, Lewis and Clark, on an epic long march.
These things are not for your general run of women, but for some they are truly possible.
They traveled in yurts with the supply train that accompanied the army.