Sauron driven out of Eriador
Event Type: Military/Strategic
Age: 2nd Age - Rings
"Sauron was driven away south-east after a great slaughter at Sarn Ford (the crossing of the Baranduin); and though strengthened by his force at Tharbad he suddenly found a host of the Númenóreans again in his rear, for Ciryatur had put a strong force ashore at the mouth of the Gwathló (Greyflood), 'where there was a small Númenórean harbor'...
In the Battle of the Gwathló Sauron was routed utterly and he himself only narrowly escaped. His small remaining force was assailed in the east of Calenardhon, and he with no more than a bodyguard fled to the region afterwards called Dagorlad (Battle Plain), whence broken and humiliated he returned to Mordor, and vowed vengeance upon Númenor. The army that was besieging Imladris was caught between Elrond and Gil-galad, and utterly destroyed. Eriador was cleared of the enemy, but lay largely in ruins."
Unfinished Tales, Part 2, Ch 4, The History of Galadriel and Celeborn: Concerning Galadriel and Celeborn