Goryeo also joined the campaign and the Khitans were exterminated .
In 1218 the Mongol and Eastern Xia armies jointly intruded into Goryeo to subdue the Khitan remnants .
Goryeo also joined the campaign and the Khitan were exterminated .
In 1218 the Mongol and Eastern Xia armies jointly intruded into Goryeo to subdue the Khitan remnants .