Who attacked the land of the Beornings during the war of the ring?

When Frodo was at Amon Hen he sat in the 'Seat of Seeing' and had lots of visions. If I remember rightly he saw the Land of the Beornings on fire.

So my question is, who could have been attacking them? It couldn't have been an attack from Dolguldur as the army from there were preoccupied with Lorien and the Woodland Realm.