Not shure what this question is exactly about.
If it is about your territory being attack when you are Away From Comp there may be a window that pops up with a set amount of reply time before an auto tribute for not accepting the fight.
If this is when loged off a notification of your territory being attacked then you should know when you are logged off you can not be attacked.
If you are looking for a large battle that might occure in World of Warcraft where alliance attacks horde and all hord get an announcement of the attack and run to kill the aliance then i am sorry to disapoint you that at this point of the game development it appears that you can not have large number of players on either side. Their is litature floating around the boards that games are currently caped at 6 players they are trying to rase the player cap to 8 players. In the MMORTS componet most litature seems to point to mainly 1 vs. 1 games of an invadeing army vs defenders home.
If i am completely wrong in my interpertation of your question then i am sorry. I would like to suggest that you check the FAQ and any questions you have be placed there so the devs can have an easier time finding our questions and may be able to get to them with official answers sooner.