quick vagely related question if you play as a different race human for example can you go to war with either dwarves or humans?
1. When you're posting on a forum, and not typing a text message on your cell, it is generally appreciated if you take the time to use proper punctuation and capitalization.
2. Depends on whether you mean officially declared war, about the modding of which I have no idea, or whether you're satisfied with a general (not formalized?) hostility, like the one exhibited by goblins towards your fortress in the unmodded game.
In short, if you want to get attacked by a civilization, then you should do the following: remove their [INTELLIGENT] tag and replace it with [CAN_CIV] and [CAN_LEARN]; the reasoning behind this is that an inability to communicate breeds hostility. I've modded my humans and elves that way, playing as dwarves, and it worked quite well.
If you want violence to really escalate, so you'll be besieged during your first summer, there's a couple things you need to do. Look for any [AMBUSHER], [SIEGER], [BABYSNATCHER], and [ITEM_THIEF] tags in your desired hostile entities, and get rid of them. I also removed [SKULKING] from my Kobolds' entry, but I'm not sure if that ever did anything in the first place. You should also set the variables on any [PROGRESS_TRIGGER] tags to 1.
The above changes are all done in the creature_standard and entity_default files.