Terrorism is the pursuit of political goals through the use of violence against non-combatants in order to dissuade them from doing what they have a lawful right to. Terrorism varies with the historical context and with the development of new technologies. Groups as diverse as the mercenaries who sacked Rome in the 16th cent., pirates who menaced the Caribbean in the 17th cent., native Americans who attacked colonists in the 18th cent., anarchists in the 19th cent., and national liberation groups in the 20th cent. were all terrorists, although their objectives and methods varied widely – Professor Philip Bobbitt