The New Testament and Pacifism

I've been really challenged since about last January trying to figure out my stance on pacifism. I agree with Hauerwas that all Christians are pacifists to some extent, but where one draws the line is how they differ. I used to think that killing for your country was okay, because that's not murder. But, as William Cavanaugh puts it, killing for a nation-state is as arbitrary as killing for the telephone company. He has a really great article, Killing for the Telephone Company: Why the Nation-State is not the keeper of Common Good.

Some verses I'm wrestling with are:
Romans 12:14 - Bless those who persecute you; bless and do not curse.
Romans 12:17a - Never pay back evil for evil to anyone...
Matthew 5:44 - But I say to you, love your neighbor and pray for those who persecute you.
Matthew 19:19b - Love your neighbor as you love yourself...

Now, those are just a few of the verses I'm trying to look over. The question in my mind is: what makes someone not my neighbor? Why is an Iraqi not my neighbor? And can I really fulfill the commandments to love if I'm shooting at someone? What would the early church have looked like if they fought back?

Practically, I think about "What if I get married and someone breaks in? Can I defend my wife?" If not, I'd say I'd rather not get married.