The use of violent and intimidating acts, especially for political ends. Terrorism has been used most commonly by revolutionary groups, whose objective is the overthrow of a particular state authority, and by nationalist groups seeking national self‐determination.

Techniques of terrorism involve bombing and shooting attacks against property and individuals, the assassination of significant persons associated with the established government or security forces, hostage‐taking, and hijacking of aircraft, trains, ships, and buses. The major objectives of terrorism are: to keep a particular cause in the forefront of public consciousness; to pressure the political authorities to concede the terrorists’ demands by inducing a state of public fear; and to induce a government to betray its own commitment to freedom and democracy by imposing illiberal security measures in order to contain such violence.

International collaboration against terrorism has not proved easy since it involves the close cooperation of legal and police authorities from many different states, which may have different international interests. The European Convention on the Suppression of Terrorism (1977), the ‘Trevi system’ of cooperation among EC members (1976), which has now spread to Council of Europe states, the Tokyo summit declaration on terrorism in 1986, and the participation of the former Soviet Union in anti‐terrorist collaboration all helped to establish a climate of international cooperation in the late 20th century. Following the attacks of September 11, 2001, the USA vigorously pursued a war on terrorism that confronted not only terrorist organizations but also so‐called state sponsors of terrorism. This interventionist and pre‐emptive approach has proved controversial.