That depends though. In Wc2, it follows the Human campaign storyline, where the Humans hold off the Orcs (thanks to Kahdgar). Too bad Lothar dies really retarded in that campaign
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However, on the Orc side, you can turn the tides by eventually leading to the eradication of Lordaeron Castle.
And the Blackrock Orcs kill Gul'dan and the Stormreaver clan themselves for ditching them in the hour of need.
In Wc3 FT, Gul'dan was actually killed by demons. But a civil war between Stormreaver, Blackrock and Twilight Hammer took place in its steed.