“Warcraft III takes place in the fictional world of Azeroth. Several years before the events of the game, a demon army known as the Burning Legion, intent on Azeroth’s destruction, corrupted a race called the Orcs, and sent them through a portal to attack Azeroth. These events were previously shown in Orcs & Humans, Tides of Darkness and Beyond the Dark Portal. After many years of fighting, the Orcs were defeated by a coalition of humans, dwarves and elves known as the Alliance; the surviving Orcs were herded into internment camps, where they seemed to lose their lust for battle. With no common enemy, a period of peace followed, but the Alliance began to fracture.

The game follows the story of three different heroes: The young and idealistic human paladin and crown prince of Lordaeron, Arthas Menethil, as he becomes more and more corrupted until he joins the Undead and assists with the summoning of demonic forces to Azeroth; the adventures of Orc warchief Thrall as he brings his people to the continent of Kalimdor to escape human captivity and the impending downfall of Lordaeron; and the events involving Tyrande Whisperwind, the Night Elven leader, who has to deal with both the arrival of humans and orcs in their sacred lands and the invasion by the demon forces.”

- Source: Wikipedia