Tunnel vision

Explanation: The Byzantine Empire and Sassanid Persians spent 26 years in their final war brutalizing each other for no real gain for either side.

A few years after they made peace, the newly united Arabian tribes under the banner of the then-new faith of Islam would entirely overrun the Sassanids, and conquer half of the Byzantine Empire.

… one can’t help but feel that the course of action taken by the two established empires was a bit self-sabotaging in this case.