Although the battle at the Wrathgate proved pivotal in erasing all tentative peace between Alliance and Horde, for a moment it appeared as though that peace would actually come to pass. Bolvar and Saurfang appeared to be almost comrades on the battlefield, fighting side-by-side with apparent respect for each other. It wasn't until Putress launched his attack on both forces that it all came crashing down -- and what the Alliance seemed all too willing to forget was that the attack was not just on us wow gold Alliance forces, but on Horde forces as well.
When Varian pushed into the Undercity, it wasn't to reclaim it for Sylvanas. It was to reclaim it for the Alliance. He had absolutely no interest in hearing about what had really occurred at the Wrathgate. He had no interest in looking at Sylvanas or the Forsaken with anything but disgust. And who can blame him? The halls of Lordaeron were once Varian's home -- they were shelter and a place of comfort after Stormwind was destroyed in selling wow accounts the First War. For that matter, Varian held absolutely no love for the orcs, and why would he -- he was just a child when he watched his father die at the hands of Garona.
If Jaina hadn't intervened, it's entirely likely either Varian or Thrall would be dead right now. And the Alliance and Horde would have wasted their time murdering each other over it instead of focusing on the real issue -- the Lich King. But there's really one moment in history that stands above all as the moment this all began ... and the ramifications of that moment continue to this day.