The Disaster of the Gladden Fields was a massacre at the beginning of the Third Age, in which Isildur and the Dunedain of Arnor, marching home after the defeat of Sauron, were ambushed by a large group of Orcs from the Misty Mountains. The king and his three eldest sons were slain and the ring was lost in the River Anduin. Only three men escaped from the attack, but the shards of Narsil were saved.

The repercussions of the attack were wide ranging, as Isildur had been king of both Gondor and Arnor, and his death left the two kingdoms to separate into isolated realms. Arnor also never really recovered from this catastrophic loss of a considerable part of its manpower.