Orgrim Doomhammer

Orgrim Doomhammer, also known as the Backstabber for his assasintion of the previous Warchief of the Horde, Blackhand,   was Warchief  of the Horde  in the final months of the First War  and throughout the entirety of the Second War . The current Horde capital of Orgrimmar is named in his honor.

Doomhammer was a brilliant leader who masterminded the assasination of the unsuccesful Warchief Blackhand and subjugation of Gul'dan's Shadow Council to the leadership of the Warchief. Upon siezing the reigns of leadership, Doomhammer successfully lead the Horde to victory over the Kingdom of Azeroth and lead the campaign against the northern kingdoms during the Second War.

Although an excellent general and warrior, Doomhammer ultimately failed in conquering humanity. The betrayal of the Sunreaver Clan and Gul'dan during the Second War, along with a number of defeats at the hands of the Alliance of Lordaeron forced the Warchief back from the outskirts of Lordaeron's capital city and eventually lead to his defeat.

Meeting with Thrall
After the defeat at Blackrock Spire, Doomhammer was captured and held as an oddity (his own words) in the palace of King Terenas Menethil II of the Kingdom of Lordaeron. However, Doomhammer was able to escape easily from Lordaeron City and made his way to an internment camp, where he saw what had become of his people. Rather than the bloodthirsty warriors he had led in battle, Doomhammer found only lethargic, wasted souls. Despairing, Doomhammer very nearly fell victim to the lethargy himself, but managed to retain enough of himself to escape from the internment camp. He lived as a hermit in the less-traveled areas of Lordaeron, until one day, he was contacted by Drek'Thar of the Frostwolf Clan.

The elder shaman informed Doomhammer that there was a young orc staying with the Frostwolves high in the mountains of Alterac. This orc, discovered to be the long-lost son of Durotan, had escaped after being raised a slave by humans and had begun searching for his people. Durotan's son, Thrall, was determined to find a way to free the captive orcs and restore them to their former glory. Orgrim had heard of this Thrall before from Grom Hellscream, whom Thrall had met before he began searching for his clan. Hellscream had nothing but good things to say about the youth.

Intrigued, Doomhammer paid a visit to the Frostwolves to see Thrall for himself, but made it clear beforehand that he didn't want Thrall to know who he was. When Doomhammer arrived nobody referred to him by name or told Thrall about him. When Thrall met Doomhammer that night, he did not realize he was dealing with the former leader of the Horde of whom he had heard so many great things; he only saw a strange orc warming himself by the fire. As the night wore on, Thrall became increasingly annoyed by the secretive demeanor of the stranger, and by his talk of how there was no point in trying to fight the humans. When Thrall insisted that the freedom of the orcs was worth fighting for, the stranger asked him what he was doing hiding in the mountains with the other Frostwolves if he really believed that. Becoming more angry, Thrall argued that he would travel south in the spring to join Grom Hellscream and the Warsong Clan, that together they would storm the camps and liberate all of the orc prisoners. The stranger scoffed at the notion and contemptuously dismissed Hellscream as a "demon-ridden dreamer." Thrall had heard enough and challenged this stranger, who had repaid the hospitality of the Frostwolves with insults, to single battle. This was precisely what Doomhammer had hoped would happen. He had implied the Frostwolves were cowards and that the orcs as a race could not defeat the humans in order to see whether Thrall would stand up for his clan and people, and Thrall had not disappointed him. Now Doomhammer would see whether Thrall's fighting skill was equally impressive.

Liberation of the orcs
Losing to the young shaman, and being shown mercy, he revealed himself as the Warchief of the Horde. At first Thrall was aghast at how he had treated such an important person as Orgrim Doomhammer, and began to apologize profusely. Orgrim stopped him and told him it was not necessary, explaining his reasons for staying anonymous. He went on to explain that he had a plan to break free the imprisoned orcs, and Thrall and Drek'thar agreed to help.

Along with Hellscream and the Warsong Clan, they were able to easily storm four internment camps freeing the orcs held inside. At the fifth, however, the Alliance was prepared and held a force of mounted knights. They ambushed the orcs and in the mist of their bloodlust the orcs fell victim to the knights' charge. In the midst of the chaos created by Thrall to cover their retreat, Orgrim was mortally wounded by a strike to the back — impaled by a charging knight's lance with enough force to pierce the back plate of his armor and his body, denting the breastplate from the inside. (This is a rather ironic death for him, since he had been called the backstabber and died being literally backstabbed). With his last breath, Orgrim gave the title of Warchief, along with his great warhammer and black armor, to Thrall.



Reference:

 http://www.wowpedia.org/Orgrim_Doomhammer