Terrorism
Terrorism is, in the broadest sense, the use of intentionally indiscriminate violence as a means to create terror among masses of people; or fear to achieve a religious or political aim. It is used in this regard primarily to refer to violence during peacetime or in war against non-combatants. The terms "terrorist" and "terrorism" originated during the French Revolution of the late 18th century but gained mainstream popularity during the U.S. presidency of Ronald Reagan (1981–89) after the 1983 Beirut barracks bombings and again after the 2001 September 11 attacks and the 2002 Bali bombings.
Unrestricted Warfare
Another instance of threats to nations within the scope of the concept of "unrestricted warfare" is terrorism. Terrorism is used by a group to gain satisfaction for certain demands. Even if these demands are not satisfied, a terrorist attack can have vastly disproportionate effects on national welfare. One only has to look at the economic crisis that followed the terrorist attacks against the United States, or the extensive security measures put in place after those same attacks. Terrorism erodes a nation's sense of security and well being, even if the direct effects of the attacks only concern a minute percentage of the population.