Defense of the Ancients is a battleground achievement based in Strand of the Ancients. To be awarded this achievement, the player's faction must prevent the opposing faction from destroying the walls protecting the beach.
As the beach walls can only be damaged through the use of siege vehicles, the first step is for the defenders to storm the beach and destroy the vehicles on the docks. Once the vehicles have been destroyed, the defenders must keep the fight on the docks to prevent the attackers from getting the use of respawning vehicles.
There is currently a perceived bias towards the Alliance, where many players have come to the conclusion that it is easier for the Alliance to accomplish this achievement. Because the Alliance is always on the attacking side first, if the Alliance team is able to quickly complete their attack, the Horde team will have a limited amount of time to attack the walls before the battleground closes, limiting the time available to damage the walls. However, when the Horde is defending, the Alliance always has a full fifteen minutes to breach the walls.