Their name is on the freaking box. The very first Warcraft product ever released is called Warcraft: Orcs & Humans. Orcs get top billing. In terms of pure history in the Warcraft setting, orcs have a lot to discuss. In their time, they've gone from a shamanistic society of hunters defending itself from the hostile gronn and ogres to a united war machine led by a figurehead, to a demon-blood drunk engine of genocide and finally out the other side, to a shamanistic society that keeps elements of the war machine alive.
Orcs are not pacifists. Like the kaldorei (night elves), orcs' view of nature is one of bloody constraint, of battle between opposing forces. Like the tauren, they respect and venerate both the hunt and the spirits of the natural world. Even the most peaceful orc, even orcs who never drank the blood of Mannoroth, are warriors and killers and hunters at heart. Orcs seek to prove themselves against the world even while struggling to find a place in it, and on Azeroth, they've found both a second chance and a new land to test themselves against.
It would be foolish to forget that orcs did what even the ancient Quel'dorei failed to do and allowed their world to be blighted and ultimately destroyed. It would also be foolish to forget that the orcish people won the First War and only lost the Second due to the greed of Gul'dan. Orcs are no simple people. Underestimate them, and you will suffer for it.
The endless ocean of the past
The early orcs inhabited a world of giants, not merely the ogres and their gronn masters (who constantly raided orc tribes for food) but the now lost grom (the word means giant in orcish, and it has been speculated that the grom were the even larger ancestors of the gronn) as well. In addition to these dangers, the orcs also had to cope with the rest of their world's flora and fauna. The home world of the orcs, which they did not name for themselves, was not a gentle one, although it did contain much of natural beauty. This combination of danger and wonder informed the development of orc society.
Orcs grew over thousands of years into a race of hunters, following migration patterns for talbuk, clefthoof and other prey animals. They also grew into a warrior race, fighting off ogre raids and even taking the fight back to the slower-witted but physically powerful enemy.
The orcish people were clever enough to understand the value of cooperation but pragmatic enough to understand that their tribal society needed a means to enforce it, and so they developed gatherings called Kosh'harg where they could meet as a people and exchange cultural ties and make friendships. The orcs Durotan and Orgrim Doomhammer forged a lifetime friendship at such a festival. The Kosh'harg was the mechanism by which orcs managed to retain a racial identity in the face of their tribal lifestyle, which led to various tribes adopting different mannerisms, customs, codes of benavior and even habits of dress. A Frostwolf from Nagrand lived a very different life from one of the orcs of the Shadowmoon Clan in their self-named valley.
Even after the coming of the Draenei, the orcs changed little. The draenei were neither hostile nor particularly interested in the orcs, leaving them to their own devices for thousands of years. The two main contributions of the draenei to orcish culture are the name for the planet, Draenor ("Exile's Refuge" in uncorrupted eredar), as the orcs had never really bothered to name their world, and the sacred mountain of Oshu'gun in Nagrand. Oshu'gun, although sacred to the orcs due to the high concentration of their ancestor's spirits that congregated around it, was in fact the crashed vehicle the naaru had used to ferry the draenei from world to world. The naaru trapped inside the crashed ship, K'ure, would become the subtle focus of the orcish religion, as the ancestor spirits drawn to him would instruct their living descendents to alter their behavior enough to ensure that he and the site of the crash would be protected. In essence, the mystery of orc shamanism was its alteration by these orc ancestors to preserve the Oshu'gun site and protect it from any who would seek to exploit it in order to defend K'ure as he slept in the natural regeneration cycle of Void and Light that all naaru experience.
Velen and the draenei saw no reason to disabuse the orcs of these notions; to them, the ship was merely a conveyance and K'ure a friend and mentor, not a religious figure. It could do no harm if the orcs wished to believe the site holy, and perhaps it even was. K'ure's presence there certainly drew the orc ancestors.
This cycle of life, where each tribe had its own set range and patrolled it in migration, coming together for the Kash'harg twice during Draenor's year, continued on seemingly unchanging and unchangeable. There was a traditional means of tribes unifying to face a great danger in what one could call a warhost or horde, but this was more observed in its abeyance than in practice. Nothing sufficient to threaten the orcish people had occurred in living memory. It may have been a remnant of the time when grom and gronn first tried to destroy the orcs, or it may simply have been a contingency never executed.
At any rate, it did not seem to be needed. The orcs communed with the spirits of their ancestors and the elements, spoke to their totems and followed the hunt. Their shamans and wizened leaders led them in the ancient ways. They traded with the strange but unthreatening draenei. Life was not easy, but it was good.
What happened next is a tragedy on many levels. Good orcs, orcs of principle who had served their people well, would be corrupted. Their very natures would be twisted. Children would be drained of life so to age them into full adulthood faster to use them as warriors, alliances with the ancient enemy would be enacted. The orcs as a people would believe the words of one who was said to be wise and yet who fell for a deception rooted in his own lust for power.
Next week, Ner'zhul, Gul'dan, and how the spirit of the orcs was forever altered.
While you don't need to have played the previous Warcraft games to enjoy World of Warcraft, a little history goes a long way toward making the game a lot more fun. Dig into even more of the lore and history behind the World of Warcraft in WoW Insider's Guide to Warcraft Lore.