Terrorism, in its broadest sense, is the use of criminal violence to provoke a state of terror or fear, mostly with the intention to achieve political or religious aims. The term is used in this regard primarily to refer to intentional violence during peacetime or in the context of war against non-combatants (mostly civilians and neutral military personnel). The terms "terrorist" and "terrorism" originated during the French Revolution of the late 18th century but became widely used internationally and gained worldwide attention in the 1970s during the Troubles in Northern Ireland, the Basque conflict, and the Israeli–Palestinian conflict. The increased use of suicide attacks from the 1980s onwards was typified by the 2001 September 11 attacks in the United States. There are various different definitions of terrorism, with no universal agreement about it. Terrorism is a charged term. It is often used with the connotation of something that is "morally wrong". Governments and non-state groups use the term to abuse or denounce opposing groups. Varied political organizations have been accused of using terrorism to achieve their objectives. These include left-wing and right-wing political organizations, nationalist groups, religious groups, revolutionaries and ruling governments. Legislation declaring terrorism a crime has been adopted in many states. When terrorism is perpetrated by nation states, it is not considered terrorism by the state conducting it, making legality a largely grey-area issue.
This strategy was used in Ireland, in Kenya, in Algeria and in Cyprus during their independence struggles.Stated motives for the September 11 attacks included inspiring more fighters to join the cause of repelling the United States from Muslim countries with a successful high-profile attack. The attacks prompted some criticism from domestic and international observers regarding perceived injustices in U.S. foreign policy that provoked the attacks, but the larger practical effect was that the United States government declared a War on Terror that resulted in substantial military engagements in several Muslim-majority countries. Various commentators have inferred that al-Qaeda expected a military response, and welcomed it as a provocation that would result in more Muslims fight the United States. Some commentators believe that the resulting anger and suspicion directed toward innocent Muslims living in Western countries and the indignities inflicted upon them by security forces and the general public also contributes to radicalization of new recruits. Despite criticism that the Iraqi government had no involvement with the September 11 attacks, Bush declared the 2003 invasion of Iraq to be part of the War on Terror. The resulting backlash and instability enabled the rise of Islamic State of Iraq and the Levant and the temporary creation of an Islamic caliphate holding territory in Iraq and Syria, until ISIL lost its territory through military defeats. Attacks used to draw international attention to struggles that are otherwise unreported have included the Palestinian airplane hijackings in 1970 and the 1975 Dutch train hostage crisis.