The past is prologue. Melodramatic, perhaps, but it bears stating. The world of Azeroth, known to us for the three most recent wars, has in fact seen many -- the War of the Ancients, the War of the Shifting Sands, the war between the ancient troll empires and the aqir. One of these wars went far to set the stage for the First and Second Wars by creating, in effect, three of the major players in those conflicts. Without the Troll Wars, there would today be no Silvermoon, no human nations (and thus no Forsaken), and the troll nation of Zul'Aman would rule all of northern Lordaeron, perhaps all the way south to Khaz Modan.
The Troll Wars were named by their victors. To the trolls of Zul'Aman, they never really ended. Pushed back by the elves of Quel'Thalas and their human allies, the once-great northern troll empire receded but never actually died. Technically, even after repeated raids by outsiders, the Amani still hold onto their ancestral home. But all around it, the direct descendants (barely two elven generations) of their conquerors hold the Ghostlands, forests scarred by the Scourge during the Third War. War seems to never leave the gates of the troll kingdoms.
However, to be fair, it's not as if the trolls are shy about warring on others, either.