I don't think that any war should be fought "under God" because extremists who initiate holy wars with what they believe to be God's blessing against those whom they see as heretics are delusional fanatics. For example, it was an Islamist extremist group of delusional fanatics who were responsible for the destruction of NYC's Twin Towers, yet there were people who chose to denounce every Muslim on the face of the earth for that act. Others, like Jerry Falwell and Pat Robertson (whom many have viewed as being instigators of Christian extremism in this country) seized the opportunity to blame America's homosexuals for the destruction of NYC's Twin Towers. How are those who used this terrible event to justify and direct their hatred against an entire people any different from the extremists who perpetrate unjustifiable death and destruction against an entire people?
I think that aggression initiated in God's name has more to do with a desire to wipe out the heretic, to "burn the witch," rather than serve as self-defense. There is no reason why the so-called godly cannot live in peace alongside the so-called heretical, unless they choose not to do so because the ways of the heretic offends them.
If someone tries to rape you, you know that they are not going to stop until they have completed the act. They may not have initially planned to kill you, but they could easily wind up killing you. I agree that nothing less than killing a person who violently violates your body like that would be an appropriate act of self-defense.