The Troll Wars were a series of conflicts between the forest trolls of the Amani Empire and an alliance of the humans of Arathor and high elves of the Kingdom of Quel'Thalas, ending approximately 2,800 years before the coming of the orcs to Azeroth.
Following the War of the Ancients, the night elves outlawed the use of all arcane magic in their forests, with execution as the penalty for use of the arcane arts. However many spellcasters did not agree with this and wanted to use their magic. Led by Dath'Remar Sunstrider these sorcerers decided to unleash a magical storm upon the tranquil forests. The Archdruid Malfurion did not want to execute so many of his own people and decided instead to banish them all from their homelands, and Dath'Remar led them across the sea to the east. These elves shrunk in height and their skin lost the dark violet hue common among their kin, and thus the Quel'Dorei, commonly known as the high elves, was born.
The elves traveled for years across the world that had been shattered by the wars with the Burning Legion, but in the end, they arrived in the lands now known as Lordaeron. Settling in the Tirisfal Glades they quickly encountered the locals, and while contact with the human tribes was sparse, the local trolls had built a great empire and attacked them on sight, quickly fueling a hateful feud between the two races.
Shortly after their settling, something evil beneath the earth started to drive some of the elves insane, so they decided to press on into troll territory. It didn't take long before the high elves founded the kingdom of Quel'Thalas in the northern forests, not knowing it was an area sacred to the trolls. The forest trolls attacked the fledgling nation in ever-increasing numbers, forcing the elves to use their strong magic. The superstitious troll warbands were frightened away and it was 4,000 years before they truly retaliated.
The Founding of Strom
The human tribes also suffered at the hands of the trolls. At the time the humans were factional people, scattered and leaderless. Chieftain Thoradin of the Arathi saw the threat to his race and decided to unite the humans. Along with his trusted friend and greatest general Ignaeus, later to be known as Trollbane, and the noble leader of Tirisfal, Lordain, he devised a cunning strategy: fight the nearby human tribes, and after each victory offer them peace and equality. With this tactic, he united the tribes of the Arathi Highlands and founded the first of the human kingdoms, Arathor. Situated in what is now known as the Hillsbrad Foothills and Arathi Highlands, his growing empire ruled from the capital city of Strom. Up to this time, the human empire had rarely had contact with the reclusive, magic-wielding elves, and all contact with the trolls was through border skirmishes.
As Quel'thalas maintained a watchful eye over their conquered forests, Trolls elsewhere on Azeroth now looked to the simmering tensions growing in the northeast. The Zandalari Tribe of Zandalar saw an opportunity to reassert Troll dominance in the east, and a group of wise Zandalari Emmisaries offered their strength and guidance to the Amani Empire. The Zandalari brought with them soldiers, strategies, even entire Loa were summoned forth from the wilderness to fight on behalf of Trollkind. Perhaps most importantly in their contributions, was the crowning of a new Amani Emperor. As the long-respected and admired Priest caste of the Troll race, the Zandalari invoked their authority to name the mighty and inspirational Jintha as the new Lord of the Forest Trolls. With their Zandalari allies close by and the blessings of dozens of loa heaped upon them, the Amani Empire girded for war.
The Siege of Quel'Thalas
Small Amani warbands emerged from the forests and began prodding the elves' defenses, testing the strength of Quel'Thalas. The cunning Trolls were sly, never revealing their true numbers, leading the elves to believe this recent movement was nothing but simple raids. After a few successful skirmishes by the Amani, The Emperor and his Zandalari advisors decided that the time for total war had come. Without warning, tens of thousands of forest trolls flooded out of the forests of Lordaeron and immediately overran the high elves' defenses, pushing them back to the Elrendar river. Monstrous Loa Demigods marched alongside the massive troll armies, infusing them with supernatural strength. The high elves struggled desperately to match this unfamiliar, wild magic, going as far to steal great magic from the Zandalari Loa Zanza the Restless and attempting to turn the Trolls own magic back upon them. All such efforts failed or merely resulted in weaker arcanum that failed to hold back the green tide. With astonishing speed and ferocity, the Amani laid waste to the defenses of Quel'thalas, while the Zandalari wise men watched the war unfold from Zul'Aman with growing pleasure. Victory seemed like only a matter of time.Aman with pleasure. Victory seemed like only a matter of time.
Alliance between Elves and Men
Throughout the war raging to the North, Emperor Thoradin had been watching the unfolding developments closely. His scouts had returned to him reporting smoke rising from Quel'Thalas' boarders, but most concerning of all was the evidence of barbarism and butchery the Trolls left behind them is a trail of high elven corpses. After years of continual besiegement by the trolls, the high elves, with defeat nearing, finally decided to seek the aid of the now-powerful humans of Arathor. The elven king Anasterian Sunstrider, a descendant of Dath'Remar, sent out their diplomats to try and negotiate the primitive humans into aiding them. Even though the elves had at times treated the humans no better than they had the trolls, Thoradin saw the danger in allowing the elf civilization to fall and agreed to an alliance.
Thoradin and his advisers conversed long into the night, and finally sent a proposal to King Anasterian Sunstrider. The Humans needed an edge to tip the balance of the war into the Elves' favor. The elves would teach one hundred humans how to wield the arcane arts of magic, while the massive armies of Strom would mobilize and join the war against the trolls. Anasterian was concerned, knowing that agreeing to teach Humans arcane magic could have long-lasting consequences of its own, but with the fate of his people riding in his hands, he consented to the Alliance. The High Elves dispatched magic tutors to Arathor and began hastily teaching their one hundred charges in the ways of magic, while over the next year, Arathor began marshaling its might to march north.
The Battle of the Alterac Mountains
The armies of Quel'thalas and Arathor engaged the trolls in a great battle at the foot of the Alterac Mountains. The battle lasted for many days, but the knights of Arathor refused to give any ground, and finally, the elven masters agreed that it was time to unleash the elven and human mages upon the trolls. Magical fires from the sky hindered the trolls' regeneration, and their morale suffered. After some hours of the magical bombardment, the remaining human and elven warriors charged the trolls, broke their lines, and forced them into a terrible rout. Even as they fled, the trolls were pursued and butchered by the merciless allied forces. The trolls' power was broken and their population decimated, the last Troll empire lay in ruins.
The trolls would never recover from this defeat. The Gurubashi Empire had been shattered by a deadly civil war, and now the Amani Empire of the forest trolls was broken. What remained of the trolls of the northern lands was forced into the wilderness. However, the war was not completely unsuccessful for the trolls, thousand of elves and humans had been slain and the remaining left completely weakened. Thoradin did initially not want his people to use magic, but he was forced to accept it so it could be utilized against the incredible troll armies arrayed against him. This led to the foundation of Dalaran, and later many other city-states.
The elves owed the humans a debt of gratitude for saving their people and ending the first major war since the Sundering and War of the Ancients. This debt laid the groundwork for the Alliance of Lordaeron and was honored during the Second War when Anduin Lothar, last descendant of the King Thoradin of Arathor, led the Alliance to war against the Orcish Horde for the second time in his life.
The humans had the largest gains of the war: they were united and they gained a debt of gratitude from the only force able to threaten them. They were initiated into the arts of magic, their technology was greatly improved and inspired by the elves (some claim the elves taught them the art of metalsmithing, though it is more likely they knew of that before the war). They also became the greatest power on the continent and were able to spread in every direction with almost nothing in their way.
Adapted from Wowpedia.