Morgoth's servants finally discovered Gondolin through the treachery of Maeglin. When Morgoth was ready, he loosed his massive army upon the doomed city. There was a great siege, but the city could not be saved, and thousands were killed. One by one the great lords of Gondolin fell, and king Turgon, disillusioned and broken-hearted, ordered all survivors to follow Tuor out through an escape tunnel when the destruction was inevitable. Only his guard stayed around him, and all who remained were killed as the white tower collapsed.