Over three years ago, on March 31, 2022, Dr. Sarah Seguin and I discussed the use of EMP’s (electromagnetic pulses) to zap hostile military drone swarms (transcript).

Recently, the British military has developed an EMP cannon to do just that.

Why are drone swarms a serious threat?

Drone swarms are resilient, with numbers potentially reaching a million units. That makes them difficult to neutralize individually. We can compare them to an anthill, where eliminating most ants is insufficient if even a few survive to complete their mission.

Traditional defenses that target one drone at a time are impractical against large swarms, especially in adverse conditions like cloud cover. Engaging swarms with one-on-one defensive drones in dogfights is technically complex and costly.

Why are EMPs deadly to drones?

EMPs overload electronics. Picture a filament antenna in your phone designed to capture a faint microwave signal. An EMP pulse surges through, spiking the signal, causing the antenna to flare like an old light bulb filament and burn out. While this is not precisely what happens, it is a useful illustration of how EMPs fry electronics.

Used for defense, EMPs are like bug spray that can disable an entire drone swarm at once.  

A successful EMP cannon has been built and tested. DefenseNews.com reports that last month, the British Army successfully used one cannon to neutralize drone swarms, addressing a growing battlefield threat.

Developed by a consortium led by Thales UK, the weapon uses high-frequency radio waves to disrupt drone electronics, causing them to crash or malfunction. In trials at the Air Defence Range in Manorbier, Wales, in April 2025, soldiers from 106 Regiment Royal Artillery defeated two drone swarms in a single engagement and immobilized over 100 drones across all tests. The weapon, effective up to 1 kilometer, can target multiple drones simultaneously and is resistant to electronic jamming.

The U.K. has invested over £40 million (US$53 million) in EMP cannon research, with each shot costing approximately 10 pence (about 13 cents). That offers a cost-effective alternative to missile-based air defense systems. The Ministry of Defence is collaborating with industry partners to advance EMP cannon capabilities for U.K. forces, aiming to integrate and operationalize this technology to counter evolving aerial threats.

But no technology is perfect

That’s why we are always in an arms race. To counter EMP cannons, drone makers can shield their electronics in a Faraday cage.

Consider your microwave oven’s Faraday cage that keeps all its microwaves inside. It also keeps all the microwaves from outside from coming in. Drones could be hardened against EMPs using conductive paint. But the paint adds weight, reducing mobility and flight time. Seguin noted that swarms rely on overwhelming defenses with cheap, lightweight units, making widespread hardening less feasible.