The Final Solution
The opening of the Dark Portal and entry into Azeroth is even more of a defining moment for the orcs than for the humans. But for older orcs (like Drek'thar), the fall of their people began about 45 years earlier, under the respected but ill-fated leader Ner'zhul. Kil'jaeden deceived him into believing that the draenei were plotting to destroy the orcs. By the time Ner'zhul realized his folly, it was too late -- Kil'jaeden made Ner'zhul's apprentice Gul'dan into the new leader and stripped Ner'zhul of his power. The orcs were already set in motion along a path of doom, and the extermination of the draenei was already underway.
If your orc character about 70 years old, he or she would have been born at about the time Kil'jaeden started to corrupt the orcs, growing up during the greatest changes in the history of their race, and witnessing their trainformation from a spiritual race into a genocidal maniacs. Such an elderly character might have early memories about about how Ner'zhul was deposed and Gul'dan came to power by uniting the clans into a single Horde and guiding his puppet Blackhand to become the first Warchief. He or she would also remember the number of shamans declining as Gul'dan taught warlock magic to more and more orcs, as well as the defining moment when Gul'dan invited all the orcs to drink the blood of Mannoroth, bringing all those who drank under control of the Burning Legion. Orgrim Doomhammer refused to drink, and Durotan even forbade the entire Frostwolf clan from drinking, which brought down great suspicion upon them.
If your character was a member of the Frostwolf clan, he would have had to watch while Durotan continued to voice opposition to the war against the draenei, the attack on Shattrath, and even the passage through the Dark Portal to conquer Azeroth. If your character was part of any other clan, however, she would have been consumed with blood rage like all the rest, and would have taken part in the horrors of the genocide, as well as the First and Second Wars. In the present time, looking back at those days, she may be filled with the same deep shame and regret, just like Drek'thar.
An orc born closer to the opening of the Dark Portal, 25 years prior to the setting of World of Warcraft, would have been raised in this bloodthirsty environment and would have been given the blood of Mannoroth as soon as possible -- unless he or she was a Frostwolf. The Frostwolves were exiled to the Alterac Mountains as soon as the Horde entered Azeroth. Here was the last remaining refuge for orcish shamanism, as Drek'thar finally turned away from the path of the warlock and regained the favor of the spirits. Thrall was also born here, around the same time that Orgrim Doomhammer killed Blackhand and made himself the new Warchief. When Durotan was killed, and his son thought lost, Drek'thar kept the Frostwolves going until Thrall finally returned many years later and brought renewal not only to the Frostwolves, but to the entire orcish race. If your character is a Frostwolf, he would be extremely proud of his leader and his people about now, having gone through a great deal of suffering in order to reach this point in history.
The rest of the orcs, however, did not fare so well. Things seemed to be going well after the First War, when the orcs headed north to finish off the humans in Lordaeron. During a time when Gul'dan was weak, Orgrim Doomhammer killed Blackhand and took over leadership of the Horde, forcing Gul'dan to submit to him. Later on, however, Gul'dan betrayed Orgrim and took off with a third of the Horde army in search of the Tomb of Sargeras. This left the door open for the newly formed Alliance to breach the ranks of the Horde plowing all the way back to the Dark Portal and destroying it. The humans reduced these orcs to slavery and kept them in internment camps, and, thus denied more access to the blood of Mannoroth, the orcs went into severe withdrawal and lethargy. Only Grom Hellscream's Warsong clan managed to remain free, hiding out in the wilds of Lordaeron, fighting the weakening listlessness of Mannoroth's blood curse until he met up with Thrall about 15 years after the end of the second war.
Let my people go
Thrall's story is not one that I could do justice to in this article, but if you're roleplaying an orc, it would do you a lot of good to know it. Check out Know Your Lore's two-part retelling of that story, and think about what your character was doing when those events were taking place. Were you fighting the withdrawal effects of the blood curse with Grom Hellscream when Thrall showed up after his escape? Were you in the Alterac Mountains with Drek'thar when Thrall returned to his clan? Were you freed by Thrall and Orgrim Doomhammer as they went from camp to camp liberating the orcs? However you met up with him, you probably traveled with the Horde in their exodus across the sea to Kalimdor -- but were you with Thrall's group or with Grom Hellscream's? Did you do when you met up with the Darkspear trolls on the islands near the Maelstrom? Did you aid the tauren in their battles with the centaurs? Or did you travel with Grom Hellscream's Warsong clan and confront the humans under Jaina Proudmoore? Did you stand with Thrall or with Grom Hellscream after Grom had once again drunk of Mannoroth's blood and tainted his clan? How did you feel when Grom slew Mannoroth and lifted the blood curse from your race? Where were you during the Battle of Mount Hyjal?
Perhaps more than any other race, the majority of the orcs can say that they shared in common most of the important experiences of the Third War (excepting of course, those elements we talked about last time involving humans and the Scourge). Since the end of that story, most of the orcs would consider Orgrimmar their new home -- but it is very important to remember that none of them could possibly have been born there, since Thrall founded new orcish nation of Durotar after defeating the Burning Legion. Older orcs would have been born in one of the regions of Draenor (which were very different prior to its becoming "Outland"), while younger orcs would have either been born somewhere in the conquered lands of Southeastern Azeroth (perhaps even the ruined Stormwind itself), or in one of the internment camps that orcs were later removed to.
Durotar has very much of a "Promised Land" feeling about it to those who believe in Thrall and in his cause -- but not all orcs are Thrall's devoted disciples. Especially if you are playing a warlock, you may live on the fringes of modern orcish society, continuing activities the Warchief has tried to forbid, including dark magic, slavery, and perhaps a lingering bloodthirstiness.
One final note: orcs sometimes have an undeserved and incorrect reputation for being incredibly stupid. This is probably caused by the image of orcish peons walking around doing menial tasks and speaking with poor grammar (i.e. "Me not that kind of orc!"). Remember: the peons who speak that way are a kind of "untouchable" class within orcish society, who are reduced to menial labor because of limited capacity, mental or otherwise. Thrall believes that they have the same potential as all the other orcs and is trying to improve their condition, but it is still unlikely that such an orc could rise to be a great adventurer just yet.
For further reading about the orcs, check out WoWWiki's mostly good (but sometimes inconsistent) information about the orcs and their various heroes, as well as the much-simplified Dramatis-Personae page on creating an orc of your very own, and if you are a member of Dramatis-Personae's roleplaying forums (as I suggest you should be), you can even read this thoroughly researched outline of various orcish clans and choose which clan your orc belongs to (or you can read about the clans on WoWWiki as well)! You may also find this updated timeline at WoWWiki useful as a reference.