Trump has given Iran 48 hours to reopen the Strait of Hormuz or face strikes on its power plants. The U.S. has a weapon purpose-built for exactly this: the BLU-114/B — a bomb that kills electricity without explosions. Here's how it works, where it's been used, what international law says about it, and what it would mean for 88 million Iranians.
The BLU-114/B is a special-purpose submunition designed to attack electrical power infrastructure without physically destroying it. Instead of explosives, it weaponises conductivity: each canister releases thousands of chemically treated carbon graphite filaments that short-circuit high-voltage equipment on contact.
The weapon is carried inside a CBU-94 cluster dispenser — a bus that releases 202 individual BLU-114/B canisters over a target area. Each drink-can-sized canister contains 147 reels of ultra-fine conductive fibre and a small parachute to orient itself during descent.
The military calls it the "soft bomb" — designed to cause maximum infrastructure disruption with minimal physical destruction. The concept is elegant: you don't need to blow up a transformer if you can make it short-circuit itself. But as every combat deployment has shown, the civilian consequences of a blackout are anything but soft.
The weapon exploits a fundamental vulnerability: air-insulated high-voltage equipment. Transformers, switching yards, and transmission lines rely on air gaps for insulation. Flood those gaps with conductive material, and the grid destroys itself.
A B-2 Spirit or F-35 drops the CBU-94 dispenser over the target — a transformer yard, switching station, or power plant substation. The dispenser orients vertically, begins spinning, and ejects all 202 canisters across a wide area.
Each drink-can-sized BLU-114/B canister deploys a small parachute that slows its descent and orients it. This ensures the filaments will be released at optimal altitude for maximum coverage of the target area.
A small explosive charge pops open each canister, unspooling 147 reels of chemically treated carbon graphite filaments. Each filament is thinner than a human hair. They float downward like conductive confetti, forming a dense cloud.
When filaments settle on high-voltage equipment — transformers, bus bars, insulators — they bridge the air gaps that normally separate conductors. Current flows through the graphite fibres, instantly vaporising them at approximately 3,500°C into ionised gas channels.
The vaporised filaments create plasma channels — sustained electric arcs between conductors. These arcs carry enormous current, causing explosive short-circuits, localised melting, and fires. If the current is strong enough, arcs can cause fragmented metal explosions.
Protection systems trip across interconnected substations. Load imbalances cascade from station to station. Within minutes, entire regions lose power. Restoration requires physically cleaning or replacing every piece of contaminated equipment — a process that took 24 hours in Serbia and 30 days in Iraq.
The filaments only work on air-insulated equipment — outdoor transformers and exposed high-voltage lines. Underground cables and gas-insulated switchgear are immune. This is why Serbia managed partial restoration within 24 hours. But Iran's grid, like most developing nations, is overwhelmingly air-insulated and above-ground.
The BLU-114/B has been deployed in three known conflicts. Each achieved its objective — and each revealed that a "non-lethal" weapon can have lethal downstream consequences.
The earliest version — cruder graphite spools delivered by Tomahawk cruise missiles — targeted Iraqi power distribution facilities. The attack disabled approximately 85% of the electricity supply. Blackouts persisted for up to 30 days, severely degrading Iraqi air defence radar and military command-and-control.
But the grid collapse cascaded into water purification and sanitation systems. The humanitarian cost was severe: estimates attributed tens of thousands of excess civilian deaths to contaminated water, sewage failures, and collapsed medical infrastructure in the months that followed. Human Rights Watch questioned the attacks' proportionality.
The refined BLU-114/B made its combat debut when F-117 Nighthawk stealth fighters dropped CBU-94 dispensers on five Serbian power plants simultaneously. Power went out across 70%+ of the country virtually instantly.
Serbian engineers managed partial restoration within 24 hours by cleaning accessible equipment and routing around contaminated substations. NATO re-attacked on 7 May with a second BLU-114/B wave. When graphite alone proved insufficient for lasting disruption, NATO escalated to conventional munitions against transformer stations and transmission lines — physical destruction that was far harder to repair.
Having faced criticism for the 1991 campaign, Coalition forces in 2003 struck only electrical distribution rather than generation facilities, and used BLU-114/B specifically to minimise permanent damage. The West Point Lieber Institute noted this as an example of choosing weapons to reduce civilian harm. Even so, Human Rights Watch documented proportionality concerns.
Iran operates approximately 400 power plant units with a total installed capacity of around 85,000 MW. Over 90% comes from gas and oil-fired thermal plants. When Trump says "starting with the biggest one first," he almost certainly means Damavand.
~40km southeast of Tehran. Powers millions of households in the capital region. Positioned near major gas pipelines.
Southeastern Iran, Kerman province.
Khuzestan province, near Ahvaz. Summer temperatures here exceed 50°C.
Persian Gulf coast. Russian-built. Only 1–2% of national electricity, but nuclear plants receive special protection under international law against attacks risking release of radioactive contamination.
Iran's grid wastes an estimated 18–23% of generated electricity through aging transmission infrastructure. Spare capacity sits at roughly 3%, versus an ideal of 25%. The grid is connected to seven neighbouring countries. A coordinated BLU-114/B attack on the substations feeding major cities could cascade into a near-total national blackout affecting 88 million people.
The BLU-114/B is called "non-lethal" because the bomb itself doesn't kill through blast or fragmentation. But every previous deployment has shown that the civilian consequences of prolonged power loss are severe — and in Iran's current circumstances, they would be compounded by four weeks of war, internet blackout, and over 1,500 civilian casualties.
Ventilators, dialysis machines, neonatal units, blood banks, and operating theatres depend on grid power. Backup generators have limited fuel — under sanctions, resupply is near-impossible. In Iraq after 1991, hospitals rapidly became public health hazards.
Electric pumps supply water to most Iranian cities. No power means no water pressure, no sewage treatment. In Tehran alone, roughly 9 million people would be affected. The 1991 Iraq precedent: cascading water failures contributed to tens of thousands of excess deaths.
Khuzestan summers exceed 50°C. Mountain regions drop below freezing at night even in March. Without heating, cooling, or refrigeration, the most vulnerable — elderly, children, hospital patients — face immediate risk.
Iran has been under internet blackout for four weeks. A grid collapse would kill remaining landline and cellular networks, leaving civilians completely unable to receive emergency warnings, coordinate evacuation, or contact family.
Continuous-process industries — petrochemicals, steel, cement — suffer catastrophic equipment damage from uncontrolled shutdowns. Under sanctions, replacing damaged industrial equipment would take years.
Iran has explicitly warned that attacks on its energy infrastructure would trigger strikes on U.S. and allied energy and desalination facilities across the Gulf. It already demonstrated this capability by striking Qatar's Ras Laffan LNG complex — which processes roughly a fifth of global LNG.
Attacking power infrastructure is not automatically a war crime — but it is not automatically legal either. International humanitarian law sets four tests that any such attack must pass. How a BLU-114/B strike on Iran would fare against each one is, at best, deeply contested.
Iran's military does rely on the national grid — but so do 88 million civilians. The U.S. DoD Law of War Manual takes the view that power stations are generally valid military targets. But the ICRC notes that in cases of doubt, objects must be presumed civilian. The Geneva Conventions draw a bright line between military objectives and civilian objects — they do not formally recognise a "dual-use" category.
Even if the grid qualifies as military, any attack must be proportionate: civilian harm cannot be "excessive in relation to the concrete and direct military advantage anticipated." The military advantage of disrupting the grid is real but limited — and opening the Strait of Hormuz is not a power grid issue. Blacking out 88 million people, including hospitals and water systems, sets an extremely high bar.
The ICRC states that IHL forbids attacks on energy infrastructure if the purpose is to force the adversary to the negotiating table or intimidate political leaders. Trump's ultimatum — "open the Strait or I destroy your power plants" — frames this explicitly as coercion. Under this standard, the purpose of the attack may be illegal even if the target is technically legitimate.
Using BLU-114/B rather than explosive munitions is itself a precaution — disabling rather than destroying. The West Point Lieber Institute has acknowledged this. But IHL also requires considering whether the military objective can be achieved by other means entirely. The Strait of Hormuz dispute could be addressed through diplomatic, economic, or more targeted military tools.
This attack also raises a separate constitutional question: Trump launched the current campaign against Iran on 28 February without congressional authorisation. Both houses of Congress rejected war powers resolutions in early March. The Brennan Center for Justice, the ACLU, and multiple constitutional scholars have described the entire military operation as unconstitutional.
If the U.S. deploys BLU-114/B weapons against Iran's power grid, it would be the largest deliberate disruption of civilian electricity supply in history — affecting more people than Iraq and Serbia combined by an order of magnitude, in a country already deep into a wartime crisis.