Morgûl Orcs (Bs."Uruk-Murgûl" or "Uruk-Dushgoi")) were those orcs that inhabited Minas Morgul. Many Morgul Orcs originally came from Barad-Dur or the Morannon but the majority were bred by the Morgûl Sorcerers and Pitmasters. Their forerunners had been bred in Gorgoroth by the End of the Second Age. After Sauron's defeat in the War of the Last Alliance, many survived in the burning plains of Gorgoroth or the Mountains of mordor. During Sauron's rest in Dol Guldur, the breeding programs for a Morgûl host were initiated by a new generation of morgûl sorcerers.
When Sauron returned to Mordor, the Tribes of Mordor were reorganised into effective tribal coalitions, the Uruk-Murgûl or Uruk-Dushgoi were one of these and finally conquered the city of Minas Ithil in T.A. 2000, which had been weakened and depopulated by the Great plague. The Morgûl Orcs fought under the command of Gothmog of Morgûl in the battle of Cair Andros, Osgiliath, Minas Tirith and several other campaigns. It it's high, Minas Morgûl was home to more than 30.000 men and Orcs, not counting additional troops who would be drawn and supplied at the City in times of great campaigns.
The Morgûl Orcs were led by Black Uruks, the first of their kind known to the Westlands.Others however were smaller Snagas, Scouts and Orcish trackers as well as Orcish mages and shamans.The Black Magic of Minas Morgûl also affected many of the orcish Denizens of the City, turning them into Morgûl Stalkers.
It has been suggested that some of the Orcs Saruman used to breed his own Orc-races at Isengard may originally have come from Minas Morgûl, however it is unsettled if these had been sent to Saruman by Sauron or if they were outcasts or deserters from Mordors armies.