If I build a defense system, whose sole purpose in life is to kill anything hostile to my interests, and it is always prepared to do so, why would it suddenly not decide to fire?
That's like saying the U.S. missile defense system won't shoot down a nuke sent from Russia because the President hasn't had the chance to say "we're at war" yet.
But, hey, if y'all are cool with me taking over an entire galactic sector in less than 56 hours from game start who am I to dissuade you.