So after several days arguing and many pages of posts, to summarise:
Armchair interrogators: the ends justify the means and therefore given the horrific nature of terrorist attacks any means, fair or foul, should be used to protect the population by gathering vital information. Torture works whatever you think about it.
The ends do not justify any foul means. Terrorism is not that significant in terms of deaths in the world and resorting to illegal activities just lowers us to their level and is counter-productive by increasing the support for terrorists and by providing dubious intelligence anyway. Torture does not work and is wrong even if it did.
Did I miss anything significant?
I've skipped the battlefield stuff and who invented what because I can't really see the point.