The third point I want to make is that what makes this terror at the moment particularly frightening, I think first is the combination of universal vulnerability and powerful weapons of destruction. Both those airplanes on September 11th, the anthrax scare and all the other speculation that all of you have seen in the days since.

Now, in any new area of conflict, offensive action always prevails in the beginning. Ever since the first person walked out of a cave millennia ago with a club in his hand, and began beating people into submission, offensive action prevails. Then after a time, someone figured out, well I could put two sticks together and stretch an animal skin over it and I would have a shield and the club wouldn't work on me any more.

All the way through to the present day, that has been the history of combat - first the club, then the shield; first the offence, then defence; that's why civilisation has survived all this time even in the nuclear age. So it is frightening now because we are in the gap, and the more dangerous the weapons, the more important it is to close quickly the gap between offensive action and the construction of an effective defence.

We have not quite closed the gap and it's especially frightening for young people who didn't even know about the Cold War. When my daughter's generation started thinking about politics, the Cold War was over, nobody talked to them about Vietnam. They didn't grow up on memories of Korea and World War II or like my generation, having drills at school where we'd go to a bomb shelter to be prepared when the Soviets dropped bombs on us, in the fond illusion that we could actually survive it.

So we have to be sensitive to the fact that there are objective reasons for people to be concerned, and we have to work very hard to close the gap. The modern world has been virtually awash in terror: since 1995 there have been twenty one hundred terrorist attacks. Before September 11th, fewer than twenty had occurred within the United States and only Oklahoma City had claimed a significant number of lives, though we've been dealing with this since the early '80s when over 240 of our Marines were killed by a suicide attack in Beirut.