Battle of Tumhalad
The battle was fought as result of a massive Orc-buildup beneath the Ered Wethrin and in the Pass of Sirion. Messengers from Círdan the Shipwright brought these tidings and a message from Círdan concerning a warning given to Círdan by the Vala Ulmo. Ulmo had told Círdan that the Elves of Nargothrond shouldn't fight abroad and stay in their fortress.
The Elves of Nargothrond, however, weren't used to battle in the open field for they had always waged a secret war, ambushing but never assaulting the forces of Morgoth. Also, the evil hosts were larger than anticipated and led by the Dragon, Glaurung.
The forces of Nargothrond couldn't withstand the assault and were driven towards the plain of Tumhalad, were most of them, including King Orodreth, were slain. Only Túrin withstood the attack of Glaurung for he wore an iron mask made by the Dwarves.
The defeat suffered by the Elves paved the road for the Sack of Nargothrond by Glaurung.