Between 1970 and 2017, 560 terrorist attacks involved explosives in letters, parcels, or packages sent in the mail or made to appear as if they were sent in the mail. 1  Terrorist attacks involving package bombs were least likely to be successful compared to attacks involving other types of weapons, with explosives detonating in 39 percent of all package bomb attacks. In comparison, 55 percent of pipe bomb attacks (excluding those sent in packages) were successful. Overall, 89 percent of all terrorist attacks worldwide during this period were successful, regardless of weapons used.

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