The author states that the campaigns of domestic political terrorists in democratic societies almost invariably emerge out of larger conflicts. Puerto Rican nationalism was the major issue responsible for terrorism in the United States during the 1970. Observers of terrorism in Italy suggest that legal changes-specifically the introduction in 1979 and 1983 of flexible judicial instruments that made it easier for militants to leave terrorist cells without fear of criminal penalties-contributed to the decline in Red Brigade terrorism. Federal Bureau of Investigation data showed a decline in the number of incidents of political terrorism in the United States of all kinds from an average of 119 per year in 1975-1977 to 12 per year in the mid-1980s and 3 per year in the 1990s. This has implications for the future of international terrorism of the kind directed against the United States by al Qaeda-a campaign that began with the February 1993 bombing of the World Trade Center.