: Sargeras possessed the human sorcerer Medivh in Azeroth. Together, Medivh and Gul'dan performed a ritual to open the Dark Portal , a dimensional rift connecting their two worlds. The Human Perspective: A Kingdom Under Siege
For the Orcs, Azeroth was a new world to conquer as their own home, Draenor, was dying. Warcraft: Orcs and Humans
: Despite their valiant efforts, the kingdom could not hold. Garona Halforcen , a half-orc spy who had gained King Llane’s trust, assassinated him, leading to the total collapse and destruction of Stormwind. The Orcish Perspective: Conquest and Victory : Sargeras possessed the human sorcerer Medivh in Azeroth
: Khadgar (Medivh’s apprentice) and Lothar eventually discovered Medivh’s betrayal. They led an assault on his tower, Karazhan, and executed him to stop the demonic influence. : Despite their valiant efforts, the kingdom could not hold
The war was not a random occurrence but the result of a long-term plot by the fallen titan , leader of the demonic Burning Legion.
The Humans of initially viewed the orcs as mere "beasts" or "monsters" from the swamps.