§ Of the Coming of Men into the West The Silmarillion

But it was said afterwards among the Eldar that when Men awoke in Hildórien at the rising of the Sun the spies of Morgoth were watchful, and tidings were soon brought to him; and this seemed to him so great a matter that secretly under shadow he himself departed from Angband, and went forth into Middle-earth, leaving to Sauron the command of the War. Of his dealings with Men the Eldar indeed knew nothing, at that time, and learnt but little afterwards; but that a darkness lay upon the hearts of Men (as the shadow of the Kinslaying and the Doom of Mandos lay upon the Noldor) they perceived clearly even in the people of the Elf-friends whom they first knew. To corrupt or destroy whatsoever arose new and fair was ever the chief desire of Morgoth; and doubtless he had this purpose also in his errand: by fear and lies to make Men the foes of the Eldar, and bring them up out of the east against Beleriand. But this design was slow to ripen, and was never wholly achieved; for Men (it is said) were at first very few in number, whereas Morgoth grew afraid of the growing power and union of the Eldar and came back to Angband, leaving behind at that time but few servants, and those of less might and cunning.