§ Of Tuor and the Fall of Gondolin The Silmarillion

At last, in the year when Eärendil was seven years old, Morgoth was ready, and he loosed upon Gondolin his Balrogs, and his Orcs, and his wolves; and with them came dragons of the brood of Glaurung, and they were become now many and terrible. The host of Morgoth came over the northern hills where the height was greatest and the watch least vigilant, and it came at night upon a time of festival, when all the people of Gondolin were upon the walls to await the rising sun, and sing their songs at its uplifting; for the morrow was the great feast that they named the Gates of Summer. But the red light mounted the hills in the north and not in the east; and there was no stay in the advance of the foe until they were beneath the very walls of Gondolin, and the city was beleaguered without hope. Of the deeds of desperate valour there done, by the chieftains of the noble houses and their warriors, and not least by Tuor, much is told in The Fall of Gondolin: of the battle of Ecthelion of the Fountain with Gothmog Lord of Balrogs in the very square of the King, where each slew the other, and of the defence of the tower of Turgon by the people of his household, until the tower was overthrown; and mighty was its fall and the fall of Turgon in its ruin.