Throughout history, the Mongols were always worried about having their base camp discovered and pillaged by enemies.
For this reason, they would always leave behind a small force to guard the camp, usually injured or older warriors and of course, women and children.
This situation is simulated in khan:
If a player manages to get a minor piece to the enemy camp (any of the 4 corner squares in enemy territory), then that piece is elevated to 'Warrior' status.
Basically the piece gains a horse and/or the weapons necessary to promote the piece to that rank.
In real life, the mongols would always leave behind extra horses and weapons, the former being their life blood.
By default, enemy base promotions are turned on.
To disable the option, go to Game..Rules.
Example base promotions:
Above, there are 2 white pieces that can promote at the enemy base, and likewise 2 for black:
promotes to
promotes to
(* piece at C7 is a magician that has been demoted to a lesser magician)
both
promote to 
Again, two white pieces that can promote at the enemy base, and likewise 2 for black:
promotes to
[*khan sword
promotes to khan archer] promotes to
[*magician
promotes to power magician] 
promotes to
promotes to
[*khan archer
promotes to khan]