Since the events of 11 September 2001, terrorism has been one of the key topics of the contemporary era. But how great is the threat of terrorism in reality? Before the attacks on the World Trade Center and the Pentagon, a number of conflict analyses had deemed the security risks posed by terrorism to be negligible; far less significant, in any case, than the threat to life and limb posed by state authoritarianism and wars between regular armies both within and between states (Scheffler 2000). But it is also beyond doubt that terrorism as a form of privatized violence that targets civilians has increased, as is evident, for example, in the attacks on New York and Washington, DC (2001), Bali (2002), Madrid (2004), Jakarta (2004/2009) and London (2005). In the future, terrorism involving biological, chemical or nuclear weapons could increase the human costs dramatically. Nonetheless, in its survey of threats to global security, the United Nations identified terrorism as just one of numerous dangers. It attached just as much importance to wars between nations, civil wars, and the production of and trade in weapons. The report also expressed the view that terrorism is a threat to some, but by no means all, countries of the world.

While the true extent of the threat posed by terrorism remains a matter of controversy, the psychological impact of this form of violence, which is practiced by underground groups, is tremendous. So far, the fear of terrorism exceeds its destructive power many times over.