Dagor-nuin-Giliath it is named, the Battle-under-Stars, for the Moon had not yet risen; and it is renowned in song. The Noldor, outnumbered and taken at unawares, were yet swiftly victorious; for the light of Aman was not yet dimmed in their eyes, and they were strong and swift, and deadly in anger, and their swords were long and terrible.
Between the time Morgoth stole the Silmarils and the Noldor got to Middle-Earth, Morgoth had raised Thangorodrim, rebuilt his armies, and fought Thingol. Morgoth hoped to obliterate the Noldor before they became firmly established, so he sent his armies towards the camp of the Noldor.
Although the Noldor were outnumbered, the Orcs were quickly defeated. A remnant of the Orcs retreated through the passes to the plain of Ard-Galen. Orc forces that had been besieging the Havens marched north to aid, but eventually were surrounded at the Fens of Serech, where all but a few were destroyed.
The host of the Noldor followed this small troop. Feanor, hoping to complete his victory and perhaps come against Morgoth himself, raced ahead with only a small group. Soon the hunter became the hunted. Balrogs from Thangorodrim were joined by the retreating Orcs. Feanor fought on alone, and finally was stricken by mortal wounds. With the arrival of his sons, the Balrogs returned to Angband. Victory was incomplete, and without glory.
Sources:
The Silmarillion (
of course)
The Atlas of Middle-Earth