[Edi]

Yes, I'd break it. There's being honorable and then there's just being goddamn stupid. I would think less of anyone who actually held to the NAP down into death and defeat if they could have made a fight of it by breaking it.

I would warn the person I was breaking the NAP with to the effect that "Sorry, would have liked to hold it but deal's done because otherwise I have no fighting chance." Doesn't mean I'd automatically break NAPs in future games. I prefer to hold to my word, but anyone who takes NAPs as ironclad restrictions that cannot ever be deviated from even when it's the only viable choice for survival is living in la-la land.