The War of Trebizond was a short and undeclared (but very bloody) war between the Sassanid Empire and the Byzantine Empire. It was started by Yazdegerd's claim over his former areas in Armenia and ended after he and Emperor Constans of Byzantium both died of mortal wounds during the last phase of the war. The sides, evenly matched, caused huge casualties between both of them; however, the war is generally considered a Sassanid victory.