Reuters reported from Dr Fox's speech that:

"We're going to have a long-term battle against transnational terrorism and it will pop up in a lot of different places over a long period and we are going to have to face up to that," he said.

One of the lessons of recent British defence history, he added, was that combat troops should not be deployed unless authorities were willing to give them the resources to carry out their work.

"That's one of the things we are grappling with in the new defence review in the UK because this will not be the last time, I would venture to guess, that we might be faced with such a situation."

There was a diminished appetite for intervention globally, but often war was not something countries had any choice about.

"No one would imagine the U.S. would have gone into Afghanistan... (but) a couple of hours in Manhattan changed things," he said, referring to the Sept. 11, 2001 attacks.

"While we can't move to a posture that is heavily weighted towards intervention to the exent that we are in Afghanistan, nor can we move to a 'fortress Britain'.. We need to maintain a balanced posture."