Here's another option for attacking w/o a formal declaration of war.

Remember that when war is declared, it continues until oneside has been
completely defeated, or diplomacy has resolved the conflict.

If neither of these conditions have been met, then you are still at war.
(I use Rhoubhe's ancient War on Humankind as a tool to allow him to attack
any time, anywhere without warning.)

So, declare war. Then never resolve it, and you can feel free to raid,
pillage, blah, blah, blah any time you want.

Remember: the rpg, is not the computer game, and you CAN do this...

Dustin Evermore