"...all those of the Quendi that came into the hands of Melkor, ere Utumno was broken, were put there in prison, and by slow arts of cruelty were corrupted and enslaved; and thus did Melkor breed the hideous race of the Orcs in envy and mockery of the Elves, of whom they were afterwards the bitterest foes."
The Mordor Barracks produces the innumerable hordes of Mordor orcs. It is one of Mordor's most essential structures because it can train free Orc Warriors. It is also the place to recruit Gothmog.
When built at a normal Mordor Outpost, the Barracks becomes an Orc Tent instead (appearance is the only difference).
Unlike many buildings of other factions, the Mordor Barracks does not have level up upgrades. Instead, it levels up as it produces orcs. It is key to note that since 4.5, Orc Warriors do not grant XP to the Mordor Barracks they are trained in. Only Orc Archers and Orc Pikemen do.
Level 2: +20% build speed
Level 3: +30% build speed
Influence of Sauron - Sauron fills a building of Mordor (excluding Tol-In-Gaurhoth and the citadel) with his will, unlocking specific effects like new units or upgrades. Fire Arrows can be researched from the Barracks for 1200 resources
The Mordor Barracks is also where you can research the Banner Carrier and Fire Arrow upgrade:
Banner Carrier - This upgrade can only be given to a level 1 battalion and will promote it to level 2. At level 2 the battalion can regenerate units when out of combat. Cost: 200
Requires Level 2
Fire Arrows - This upgrades adds a bonus FIRE damage to the unit. Causing it to deal increased damage to everything and even more to buildings. Cost: 400