An EMP attack in Sweden could disable electricity, communications and transport systems across large areas within a fraction of a second, without producing a conventional explosion at ground level. Swedish defence authorities are now increasing tests of military equipment as nuclear arsenals are modernised and the country reassesses its exposure to electromagnetic threats.
An electromagnetic pulse, usually shortened to EMP, is an intense burst of electromagnetic energy. In the scenario examined by Swedish authorities, it would be generated by a nuclear weapon detonated at high altitude, above the atmosphere.
At that altitude, the weapon’s blast and radioactive fallout would not directly reach the ground. The resulting electromagnetic pulse could instead create powerful electrical currents in cables, antennas and electronic systems, damaging or disabling equipment over a wide geographical area.
The pulse would not directly injure people. However, a prolonged failure of electricity, hospitals, water supplies, emergency communications and transport could still place lives at risk.
How an EMP attack in Sweden could work
The effects of a high-altitude nuclear EMP would depend on the weapon’s explosive yield and the altitude at which it was detonated.
According to the Swedish Defence Research Agency (Totalförsvarets forskningsinstitut, FOI), an electromagnetic pulse can damage critical electronic systems and networks even though it does not directly harm the human body. A recent FOI report warned that the consequences could be significant for Sweden’s healthcare system.
Modern infrastructure relies on interconnected electronic components. Electricity networks, mobile communications, digital payment systems, traffic controls and emergency services could therefore be affected simultaneously.
Long cables and antennas can act as conductors, allowing the pulse to generate sudden electrical currents. Components that have not been shielded against electromagnetic interference could be damaged immediately.
Swedish public broadcaster SVT reported that even the country’s outdoor warning sirens, commonly known as Hesa Fredrik, might stop working. Henrik Larsson, acting head of population protection at the Swedish Civil Defence Agency (Myndigheten för civilt försvar), said an EMP event would have an extensive impact on society and could prevent authorities from using air-raid warnings.
Although Swedish civil defence shelters are designed to resist an electromagnetic pulse, reaching them or organising evacuations could become difficult. Digital communications could fail and many modern vehicles might no longer operate reliably.
Sweden has limited civilian protection
Sweden has extensive experience in military and civil defence planning, but its civilian infrastructure has not been systematically protected against a large-scale electromagnetic pulse.
Effective protection requires several measures. Sensitive systems can be enclosed in conductive shielding, cables can be fitted with protective components and institutions can retain analogue or mechanically operated alternatives.
Such measures are generally easier to incorporate when infrastructure is designed than when they are added later. Protecting every electronic device is also neither realistic nor necessary. Authorities instead have to identify the systems required to maintain essential services during a prolonged emergency.
Analogue reserve systems could become particularly important. Emergency radio networks, manual procedures, backup generators and vehicles with fewer electronic components could allow some services to continue operating.
The vulnerability reflects a broader problem across highly digitalised countries. Digital systems improve efficiency during normal conditions but can create common points of failure when electricity and communications are disrupted at the same time.
Military equipment is being tested more frequently
The Swedish Defence Materiel Administration (Försvarets materielverk, FMV) operates facilities capable of simulating the electromagnetic conditions produced by a nuclear explosion.
At one testing facility, military vehicles, artillery systems and ammunition containers are exposed to controlled pulses. Engineers can then assess whether shielding and other protective measures allow the equipment to continue operating.
FMV publicly lists an electromagnetic pulse test facility, together with microwave, lightning and electromagnetic interference laboratories, among its testing infrastructure. Its Test and Evaluation division is responsible for assessing technical systems used by the Swedish Armed Forces.
SVT reported that testing has increased as Sweden’s security environment has deteriorated. Fredrik Nielsen, an FOI researcher specialising in electromagnetic pulses, said interest in the issue had changed considerably since Russia’s full-scale invasion of Ukraine.
Military forces increasingly depend on electronic equipment for communications, navigation, sensors and weapons systems. Even ammunition may contain advanced electronic components, making electromagnetic protection relevant throughout the defence supply chain.
Sweden is now considered a possible target
During the Cold War, Swedish defence planners did not generally consider the country a primary target for a dedicated EMP attack.
They nevertheless recognised that Sweden could suffer disruption from a nuclear detonation aimed elsewhere because a high-altitude pulse can cover a very large area. Swedish planners referred to this as the “bystander scenario”.
According to Nielsen, that assessment has changed. Swedish experts now consider that the country itself could be selected as a target for an electromagnetic attack.
No nuclear EMP weapon has been used during an armed conflict. The absence of previous attacks makes it difficult to calculate precisely how current infrastructure would respond, particularly because electricity networks and digital systems have become far more complex and interconnected.
An EMP attack would also cross the boundaries between nuclear deterrence, cyber security and civil preparedness. Its immediate effects would be physical, but many consequences would resemble a simultaneous cyberattack against thousands of systems.
For Sweden and its Nordic neighbours, preparedness therefore depends not only on military equipment. It also requires resilient electricity grids, protected communications and procedures that can function without constant digital access.
Sweden’s expanding tests show that the electromagnetic threat is no longer treated only as a Cold War scenario. The central challenge is now determining which systems must continue operating when much of the technology on which society depends suddenly stops working.
