"When the world's strongest military power (the US) suffered a terrible attack almost six years ago-brought about not by another superpower, but a bunch of radicals based in Afghanistan, we realized that deterrence had failed, " he added.
Addressing the International Institute for Strategic Studies' (IISS) 5th Global Strategic Review (GSR), De Hoop Scheffer added that he believes that September 11 dealt the blow to the old, Cold War paradigm with its Eurocentric view of the world.
"It demonstrated that in the wake of economic globalization, threats too are globalising: terrorism, failing states and the proliferation of weapons of mass destruction are global phenomena that cannot be met with purely national or even regional approaches," he stressed.
Against these threats, De Hoop Scheffer noted, a passive deterrence based strategy is of no use at all.
He stressed that not all security challenges require military solutions, but military competence remains crucial for dealing with many of them.
"Without military force, the atrocities in the Balkans could not have been stopped, and Al Qaeda would still enjoy a safe haven in Afghanistan," said the NATO Secretary-General.
De Hoop Scheffer said that the growing importance of energy security is something obvious.
He added that Osama bin Laden has described refineries as the hinges of the world's economy.
"For all these reasons, having discussions in NATO about missile defense, cyber defense or energy security is not an academic exercise. These issues are very real and very urgent. If we want to shape events and not be their victims, we must address them now," he stressed.
