The world of Azeroth has seen countless invasions, world-ending events, and massive wars. Perhaps the most important events to shape the history of Warcraft are the four great wars that pitted the factions of Azeroth against each other. These wars saw the destruction of cities, the rise of powerful villains, and the death of various characters. They each changed the trajectory of Azeroth and brought Warcraft to where it is today.
The First and Second Wars were covered during Warcraft: Orcs & Humans and Warcraft 2: Tides of Darkness. Both wars saw the creation of the modern-day Horde and Alliance, as well as the rise of characters like Thrall and Khadgar alongside the downfall of characters like Gul'dan and Medivh. These two wars caused immense change, but the Third War may have shaken up Azeroth even more.
The Beginning of Warcraft's Third War
Several years after the Horde led by Ner'zhul were defeated in Warcraft 2: Beyond the Dark Portal, a new war began to brew. Ner'zhul's soul was tortured and encased in a suit of armor by the demon lord Kil'jaeden. He then sent the armored soul of Ner'zhul to Azeroth to sit upon the Frozen Throne, giving birth to the first Lich King and leading to the first major player in the Third War. The crisis quickly began.
The events of The Third War are presented in Warcraft 3: Reign of Chaos, and begin with orc Warchief Thrall. Thrall receives a vision of an unknown prophet who tells him that he must move his new Horde to Kalimdor to escape the coming destruction. Thrall trusts the prophet and gathers his Horde, fighting through the troops of Lordaeron and sailing west to freedom. He hopes that he can find a home for his Horde away from the Alliance, a place they can be safe.
Arthas' Descent Into Evil
In Lordaeron, rumors began to spread about a plague that was infecting the northern lands, but the army was busy dealing with the Horde's escape to Kalimdor. The prophet appears once more, this time in front of King Terenas, and tells him that he too must flee west. However, Terenas proved to be a stubborn man and declared that he would defend his kingdom. He tasked his son Arthas Menethil to investigate the north alongside the paladin Sir Uther the Lightbringer and Jaina Proudmoore from the Kirin Tor.
The trio arrived in the town of Andorhal were they discovered that the grain had been infected with plague, turning humans into undead monsters. They quickly got to work fighting through the infected city, destroying the grain and hunting down the responsible necromancer: Kel'Thuzad. Once they caught the necromancer he informed them that he was simply a pawn, the true power coming from a dreadlord named Mal'Ganis. So, Arthas slew Kel'Thuzad and vowed to hunt down Mal'Ganis.
After fighting through many infected, they arrived in Stratholme, where they discovered that the infected grain had already been distributed to the townspeople. Arthas ordered Uther and his paladins to destroy the town and kill everyone inside. Uther was appalled and refused, so Arthas disbanded Uther's Knights of the Silver Hand and took anyone still loyal to him to slaughter the town.
Arthas continued this quest to cull every infected city he could find before setting his sights on finding the powerful runeblade Frostmourne, with the help of the dwarf Muradin Bronzebeard. Together they found the blade and Arthas led an assault on the Scourge base, killing Mal'Ganis. Months after his victory against Mal'Ganis, Arthas returned home and slew his father, King Terenas. He crowned himself King of Lordaeron and gave the land to the Scourge; Arthas was gone and replaced by a puppet of The Lich King.
Arthas went on a crusade after killing his father, his main mission to bring back Kel'Thuzad and take the Lich King's place. He killed Uther and marched on the High Elf capital of Silvermoon. There he met Sylvanas Windrunner, whom he slew and resurrected as the first Banshee. The Scourge slaughtered the high elves and Arthas used their source of power, the Sunwell, to revive Kel'Thuzad. Arthas then marched on Dalaran, obtained the Book of Medivh, and summoned Archimonde and The Burning Legion into Azeroth. The Burning Legion set their sights on the World Tree of Nordrassil, and the citizens of Azerorth mounted a defense.
The Night Elf and Orc Conflict in Kalimdor
In Kalimdor, Thrall's Horde were facing problems of their own. Upon arriving in Kalimdor they recruited the Tauren to their cause and left the Orcish Warsong Clan to build a settlement in the land of Ashenvale. The Night Elves and their demigod, Cenarius, did not take kindly to this and attacked them. The leader of the Warsong Clan, Grom Hellscream, drank the blood of the Legion pit lord Mannoroth, granting him immense power to kill Cenarius, but binding his clan to the Legion.
Jaina Proudmoore allied herself with Thrall to help him break The Burning Legion's control over the Warsong Clan. Together, with the guidance of the unknown prophet, they captured Grom Hellscream. Thrall and Jaina cleansed Grom's soul of the demonic taint, pulling him away from the Legion's control. Then, Thrall and Grom challenged Mannoroth and destroyed him, freeing the orcs from control. Grom Hellscream lost his life in the process, but his people were free.
The Final Battle of The Third War
Tyrande Whisperwind, leader of the Night Elves, reawakened the sleeping Elf Druids - including Malfurion Stormrage - and freed Malfurion's brother Illidan from prison. Illidan specializes in killing demons, and he confronted Arthas, who told him of a powerful artifact called the Skull of Gul'dan. Illidan took Arthas' bait and went to find the skull, which he consumes and gains immense power to kill Tichondrius, leader of the dreadlords. Doing so helped seal the Legion's defeat, but it also corrupted Illidan into a demon/night elf hybrid.
The final battle of The Third War is set as the mortals create an uneasy alliance under the guidance of the prophet, who reveals himself to be the spirit of Medivh. A large battle ensues, known as the Battle of Mount Hyjal, and using the power of the World Tree and ancestral spirits Malfurion destroyed Archimonde and his Legion in a massive explosion. The mortals reigned victorious, but the World Tree was destroyed and the Night Elves lost their immortality.
Thus, the Third War of Azeroth was over and peace reigned. However, fans of Warcraft know that peace does not last forever in Azeroth, and the forces would once again rise in various World of Warcraft expansions. For now however, the citizens of Azeroth could rest, and World of Warcraft could have a moment of peace.