LONDON -- Five years since 9/11, and we are still being told that the world has changed forever. But the attack on the United States on Sept. 11, 2001, was a low-probability event that could just as easily not have happened. The often careless and sometimes incompetent hijackers might have been caught before boarding those planes, and there were not 10 other plots of similar magnitude stacked up behind them. Would the world really be all that different now if there had been no 9/11?

There would have been no invasion of Afghanistan, and probably no second term for President George W. Bush, whose main political asset for the past five years has been his claim to be leading the U.S. in a Global War on Terror. Deprived of the opportunity to posture as a heroic war leader in the mold of Winston Churchill or Franklin D. Roosevelt, Bush would have had great difficulty in persuading the American public that his first-term achievements merited a second one.

Would Bush, Cheney, Rumsfeld, Wolfowitz & Co. have succeeded in invading Iraq anyway? That was high on their agenda from the moment they took office, but without the 9/11 attacks eight months later, they would have had great difficulty in persuading the American public that invading Iraq, a country on the other side of the world that posed no threat to the U.S., was a good idea. Whereas after 9/11, it was easy to sell the project to geographically challenged Americans: Maybe no Iraqis were involved in 9/11, but they're all Arabs, aren't they?