Battle of Sudden Flame
The Battle of Sudden Flame (Dagor Bragollach) was the fourth great battle of the Wars of Beleriand.
After the Glorious Battle almost 400 years earlier, there had been a period of relative calm called the Long Peace, marked by the Siege of Angband and the prospering of the Elves and Men of Beleriand.
For that period, Morgoth had been secretly building his strength, bolstering his forces, and biding his time.
Then, in the year 455 of the First Age, Morgoth sent out rivers of flame from the Thangorodrim mountains, killing many Elves. The whole range of peaks turned into massive volcanoes spewing forth deadly fumes and burning fires, annihilating the plains south of the mountains even unto Dorthonion.
Morgoth sent out his forces once more, with Belryg and multitudes of Orcs slaughtering any they came across.
The highlands of Dorthonion, long a bastion of the Free Peoples, became completely overrun with Orcs. Two of Galadriel's brothers, Angrod and Aegnor were both killed in this battle, and her third brother Finrod Felagund was barely saved by Men of the Edain.
In the aftermath of the battle, High King Fingolfin too perished, after challenging Morgoth to single combat. Though he wounded the Dark Lord, he was unable to overcome Morgoth's titanic strength.