In the beginning, they were simple: artillery shells buried in the road, detonated by a pressure plate or a remote control device. As the wars in Iraq and Afghanistan dragged on, they became sophisticated: complex chains of explosives triggered by cell phones, infrared sensors, or multiple backup detonation systems designed to defeat countermeasures.

The improvised explosive device—the IED—became the dominant weapon of insurgent and terrorist groups in Iraq and Afghanistan. It was inexpensive to produce, impossible to predict completely, and devastatingly effective against vehicles and personnel.

The statistics tell the story. In Iraq, from 2003 to 2011, IEDs were responsible for approximately 60% of American combat deaths. In Afghanistan, the number was similar. No other weapon system was more lethal to American forces. Not small arms fire, not RPGs, not mortar attacks. IEDs killed more Americans than all other causes combined.

The military's response was dramatic. In 2006, the Pentagon created the Joint IED Defeat Organization (JIEDDO), a new command dedicated entirely to fighting the IED threat. JIEDDO became the operational heart of the technological response to the insurgency. It funded research into detection technologies, electronic countermeasures, protective armor, and tactics to mitigate the threat.

One of the most visible results was the Mine Resistant Ambush Protected vehicle, the MRAP. These were heavily armored, V-shaped vehicles designed to direct blast energy away from the occupants. The MRAP was not designed to stop an IED—it was designed to survive one. The vehicles cost $500,000 to $1 million each. By 2008, the military had deployed over 20,000 of them to Iraq and Afghanistan.

The MRAP saved lives. There is no question about that. Soldiers who would have died in Humvees survived IED attacks in MRAPs. But the evolution of the IED kept pace with the countermeasures. As insurgents saw their simple roadside bombs defeated by armor and electronic warfare, they innovated. They combined IEDs into complex ambushes. They used multiple explosives sequentially to defeat MRAP armor. They created explosively formed projectiles that could penetrate armor designed for blast protection.

It was an arms race, and like all arms races, it never quite ended. Each new countermeasure was met with an adaptation. The Americans deployed IED-sniffing dogs, so the insurgents used electronics-free detonation systems. The Americans deployed electronic warfare to jam remote detonators, so the insurgents used cell phones with delay timers. The Americans armored their vehicles, so the insurgents made bigger bombs or targeted from the sides where armor was lighter.

The human cost was staggering. A soldier or Marine who survived an IED attack often sustained traumatic brain injuries that might not be immediately apparent. The blast waves from explosions caused internal damage to the brain, sometimes leading to lifelong cognitive and behavioral problems. Thousands of veterans returned home with traumatic brain injuries that would affect the rest of their lives.

The tactical impact was also profound. IEDs didn't need to kill anyone to be effective. The mere presence of IEDs, or the threat of them, shaped how American forces could operate. Units had to slow down to check roads. Convoys had to spread out to reduce the impact of simultaneous explosions. Every culvert, every pile of trash, every disturbed patch of earth had to be treated as a potential threat.

This changed the nature of counterinsurgency. In traditional counterinsurgency, troops move through the population, interact with locals, build relationships, and gather intelligence. IEDs made that much more difficult. When every movement might result in an explosion, soldiers are naturally more cautious, more distant, more likely to rely on heavy firepower and less likely to engage in the nuanced work of building trust with the population.

By the end of the wars, IEDs had killed over 3,000 American service members and wounded tens of thousands more. They had shaped tactics, strategy, procurement decisions, and medical protocols. They had inspired technological innovation and driven defense spending. They represented the core challenge of asymmetric warfare: an opponent with fewer resources and less advanced technology finding ways to inflict disproportionate casualties on a technologically superior force.