Gang Warfare in GTA San Andreas
Gang Warfare is when gangs fight over a territory. It is an available sub-job in Grand Theft Auto: San Andreas.
In it, "CJ" shoots a number of enemy gang members (3-4) for it to start. 3 waves of enemies swarm in at diffeent times to stop you. If you loose, the territory can either go back to the enemy, or its color can be taken down, no longer being territory. If the latter happens, enemies still walk/drive around and so it is reclaimable.
A defencive gang war is when the enemy gang attacks your territories. Instead of three waves, the gang is already there. If you die or stay away, the territory can be taken over by enemies.