§ Of the Ruin of Doriath The Silmarillion

Thus it was that the host of the Naugrim crossing over Aros passed unhindered into the woods of Doriath; and none withstood them, for they were many and fierce, and the captains of the Grey-elves were cast into doubt and despair, and went hither and thither purposeless. But the Dwarves held on their way, and passed over the great bridge, and entered into Menegroth; and there befell a thing most grievous among the sorrowful deeds of the Elder Days. For there was battle in the Thousand Caves, and many Elves and Dwarves were slain; and it has not been forgotten. But the Dwarves were victorious, and the halls of Thingol were ransacked and plundered. There fell Mablung of the Heavy Hand before the doors of the treasury wherein lay the Nauglamír; and the Silmaril was taken.