: " Those who believe that the Orcs were bred from some kind of Men, captured and perverted by Melkor, assert that it was impossible for the Quendi to have known of Orcs before the Separation and departure of the Eldar. For though the time of the Awakening of Men is not known, even the calculations of the loremasters that place it earliest do not assign it a date long before the Great March began, certaintly not long enough before it allowed for the corruption of Men into Orcs. On the other hand, it is plain that soon after his return Morgoth had at his command great numbers of these creatures, with whom he ere long began to attack the Elves. There was still less time between his return and these first assaults for the breeding of Orcs and for the transfer of thier hosts westward"

: To make this short, from what I read in HOME X:
: Orcs were bred from Men, and if 'the conception in mind of the Orcs may go back far into the night of Melkor's thought' it was Sauron who, during the ages of Melkor's captivity in Aman, brought into being the black armies that were available to his Master when he returned.
: Although, this hypothesis doesn't hold up well against the chronolgy of the Awakening of Men around the time the Sun first rose.