From Kotaku:

In a battle six months in the making, members of the Destruction faction on European server Karak Eight Peaks laid siege to the Order capitol Altdorf. After a running 14-hour battle spent systematically taking over the city piece-by-piece, Destruction faced off against Order's leader Karl Franz and came out triumphant, capturing the city and placing the fallen king in a cage, all without using the exploits that made earlier successful sieges null and void.

For the many of you who've given Warhammer Online a pass, this is probably one of the biggest achievements the game has to offer. Having been playing the game on and off over the past month, I imagine the Destruction pride on that particular server must be completely unbearable at this point. Still, the best side won.
I really must try this game now that they are offering a free trial.