§ Of the Coming of Men into the West The Silmarillion

But many Men remained in Estolad, and there was still a mingled people living there long years after, until in the ruin of Beleriand they were overwhelmed or fled back into the East. For beside the old who deemed that their wandering days were over there were not a few who desired to go their own ways, and they feared the Eldar and the light of their eyes; and then dissensions awoke among the Edain, in which the shadow of Morgoth may be discerned, for certain it is that he knew of the coming of Men into Beleriand and of their growing friendship with the Elves.