Orcs of Mordor
 Second Age
After Sauron established himself in the Black Land of Mordor around S.A. 1000, he took under his command countless Orcs that continued to battle with Elves and Men over many centuries. The Orcs of Mordor were not simply gathered from the remnants of Morgoth's armies, but were also bred anew by Sauron.
When Sauron learned of the Last Alliance, he sent many Orcs from Mordor to ambush the Allied forces who would cross the Misty Mountains, but they were too strong and the Orcs hid themselves. That small detachment was eventually forgotten and it's possible they mingled with the Orcs of the Misty Mountains.
 Third Age
There were many types in the service of the Red Eye, but the largest and fiercest were the Uruks of Mordor, black Orcs of tremendous strength and ferocity first seen out of Mordor around T.A. 2475, assaulting Ithilien. Ithilien was re-taken by Steward Boromir, but years later Ithilien was infested again by Mordor-orcs driving most of the people west of the Anduin.
It seems that Sauron could breed armies of Orcs with enormous speed when they were needed. According to Aragorn, for instance, it had taken just a few years for the Orcs to multiply in Mordor to the vast hordes seen in the War of the Ring.
In February of T.A. 3019 a group of Mordor-orcs under Grishnákh joined forces of the Orcs of Isengard on the plains of Rohan during the War of the Ring. Those raided and captured Merry and Pippin. Those Orcs then attempted to head east, but returned when they noticed Rohirrim approaching. Eventually they were wiped out by them.
Orcs made up the backbone of the Eastern hordes during this War, supplemented by Easterlings, Haradrim, and monstrous creatures of Sauron.
Following Sauron's final defeat at the end of the Third Age, Western forces cleared the Black Gate and surrounding hills of Orcs easily without their master to guide them, though it is suggested many escaped into the vast wastes and steppes of Mordor's eastern lands.
- ↑ The nature of those wars and if they were related to the Orcs of Mordor is not clear. In the Unfinished Tales it is said that Egalmoth was unable to support Rohan in T.A. 2710; although the reason is not explained, it could be the Orc-wars. On the other hand, Christopher Tolkien connects the Orc-wars to the Orc invansions of Eriador 3 decades later (T.A. 2740).
- ↑ J.R.R. Tolkien, The Lord of the Rings, Appendix B, "The Second Age"
- ↑ J.R.R. Tolkien, Christopher Tolkien (ed.), Unfinished Tales, "The Disaster of the Gladden Fields"
- ↑ J.R.R. Tolkien, The Lord of the Rings, Appendix A, "The Númenorean Kings", "Gondor and the Heirs of Anárion", "The Stewards"
- ↑ J.R.R. Tolkien, Christopher Tolkien (ed.), The Peoples of Middle-earth, "VII. The Heirs of Elendil"
- ↑ J.R.R. Tolkien, The Lord of the Rings, The Fellowship of the Ring, "The Great River"
- ↑ J.R.R. Tolkien, The Lord of the Rings, The Two Towers, "The Uruk-hai"