Military action
Nasir and Arcanaan remained locked in constant warfare with each other for hundreds of years. The drawn-out hostilities eventually end in a stalemate.
The border fluctuates during this time after every encounter but ultimately cuts east-to-west between the northern and southern ranges of the Numir Mountains--with some degree of latitudinal variance that was never fully agreed to by either side. At the end of it all, the imperial province of Tavarin (which saw the most fighting) lost almost half of its total land with the southern panhandle falling under total Dominion control.