Defenders can significantly slow down the attack on the general by attacking players, assisting NPCs, attempting to capture graveyards, or other forms of disruption. A common defensive tactic is to attack the gathered enemy force outside the fortress from the fortress entrance, and then run back into the fortress by the general and hide. This can be countered by crowd control / movement impairing abilities such as fear, entangling roots, polymorph, and stuns. In close matches, defense is key in delaying the enemy's attempt on your general while your attackers are simultaneously attacking their general.
Defenders with a Stormpike Insignia or Frostwolf Insignia can use it repeatedly to teleport just outside the fortress entrance. This can teleport you near your general to defend them.