John Wayne was just ahead of his time
with this casting.
Today anybody can play anybody.
Samuel L. Jackson can play Nick Fury, etc...
On the one hand it's admirable that John Wayne, whom a lot of Americans considered to be their tough hero in 1956, would play a Mongolian warlord. In many ways that's a big compliment.
Sig, you want a sig, here's a SIG-sauer!