With Cataclysm bringing us closer and closer to all-out war between the Horde and the Alliance (again), I felt it was important to take a look back at the times when those two factions transcended their differences and united to fight a common enemy.  This topic was suggested to me over Twitter by @Sylus from The World of Sylus.

The first (covered below), and most obvious, was the Third War (Warcraft III). Certainly, there was conflict between the Horde and the Alliance leading up to that event, but no one can doubt that the unity seen atop Hyjal in defense of Nordrassil wasn't an epic event.

I will cover other events, such as the opening of the Gates of Ahn'Qiraj, the defense of Quel'Danas, and even the ill-fated Wrathgate offensive, in later articles. For now, however, let us start not at the beginning, but at a beginning.

The Battle of Mount Hyjal

Perhaps the singular most important example of Horde and Alliance unity happened on the slopes of Mount Hyjal, the sacred World Tree protected by the night elves. It is this World Tree, known as Nordrassil, that was planted over the second Well of Eternity in order to mask its arcane energies from the Burning Legion.

It didn't quite work, obviously, but Nordrassil still became an extremely important part of the world. It was blessed by three of the five dragonflights, and it even granted the kaldorei their immortality.

During the Third War, the Burning Legion invaded Kalimdor and pushed their demonic forces up Hyjal and towards the World Tree. Indeed, the demon lord, Archimonde, successfully reached the tree before being defeated by the sacrifice of thousands of forest spirits and Nordrassil itself.

Archimonde's bones remain here, tangled within Nordrassil's roots.

However, what should never be overlooked was the unity between the Horde and the Alliance during this time. The Burning Legion had become the common enemy, and Thrall, Jaina, and even Malfurion and Tyrande recognized the need to set aside differences and push back the Legion's thrust.

Under Medivh's guidance, Thrall and Jaina Proudmoore - the leader of the human forces in Kalimdor - realized that they had to put aside their differences. Similarly, the night elves, led by Malfurion and Tyrande, agreed that they must unite if they hoped to defend the World Tree. Unified in purpose, the races of Azeroth worked together to fortify the World Tree's energies to their utmost. Empowered by the very strength of the world, Malfurion succeeded in unleashing Nordrassil's primal fury, utterly destroying Archimonde and severing the Legion's anchor to the Well of Eternity. The final battle shook the continent of Kalimdor to its roots. Unable to draw power from the Well itself, the Burning Legion crumbled under the combined might of the mortal armies.

It was an immense battle with many deaths, but it became a landmark not just because of the victory over the Legion, but because of the victory over petty squabbles and old prejudices.

Yet, as we move into the future of the Warcraft setting, with Cataclysm on the horizon, will we see another unification like that which happened at the Battle for Mount Hyjal? Jaina and Thrall both have sacrificed much in their pursuit of peace, but dissident factions on both sides seek to upset that peace.

Indeed, there are even some humans who believe that the Burning Legion's return to Azeroth is the fault of the orcs. They claim the orcish invasion during the First War as the precedent for demon and orc collaboration, and they turn a blind eye towards the great strides made by Thrall towards building a functioning society.

If the collision course between Varian Wrynn and Garrosh Hellscream isn't diverted soon, landmark battles such as the Battle of Mount Hyjal will be nothing more than a page in the books of history.