§ Of the Fifth Battle: Nirnaeth Arnoediad The Silmarillion

Now Morgoth, who knew much of what was done and designed by his enemies, chose his hour, and trusting in his treacherous servants to hold back Maedhros and prevent the union of his foes he sent a force seeming great (and yet but part of all that he had made ready) towards Hithlum; and they were clad all in dun raiment and showed no naked steel, and thus were already far over the sands of Anfauglith before their approach was seen.