The threat from extremists who attempt to use improvised explosive devices (IEDs) to cause harm is persistent and pervasive. High-profile international incidents frequently make the headlines, yet explosive occurrences are rising sharply here in the U.S. as well. According to Justice Department statistics, there were 428 incidents in 2020, up 71% from the year before. The threat to Americans will likely remain high over the coming decade as instructions and materials for IEDs are readily available online.