Final answer:
An improvised explosive device (IED) is a homemade bomb used unconventionally by groups like al-Qaeda and ISIS to causes widespread harm. Barrel bombs are a simple form of IEDs. Metal detectors are key in preventing their damage.
Step-by-step explanation:
An improvised explosive device (IED) refers to a homemade bomb crafted and deployed in methods that differ from formal military tactics. These devices are notoriously unpredictable and can cause significant harm to both military targets and civilians. For instance, the 'barrel bombs' mentioned may contain explosives and shrapnel, like nails, and are austerely designed compared to more sophisticated chemical weapons utilised by advanced military forces. The usage of IEDs by nonstate or nongovernmental organizations, such as terrorist groups like al-Qaeda and ISIS, represents a paradigm shift in global security threats. These groups, which operate as loosely connected cells across various continents, have leveraged IEDs as strategic tools to project power and spread terror beyond conventional battlefields.
Countermeasures to IEDs include the application of metal detectors by soldiers to locate and neutralize potential threats. Such preventative initiatives are crucial in maintaining the safety of military personnel and civilians in conflict zones.