What is the 'mother of all bombs' the US could use against Iran?

The United States is considering using its most powerful non-nuclear bomb against Iran as President Donald Trump weighs renewed military strikes, raising questions about its devastating impact and whether it could penetrate Tehran's heavily fortified nuclear facilities.

According to a CNN report on Thursday, US military planners have drawn up options involving the GBU-43/B Massive Ordnance Air Blast bomb, commonly known as the "mother of all bombs" or MOAB, to target Iranian energy infrastructure and nuclear sites.

The plans reportedly include possible strikes on Pickaxe Mountain, an underground facility near Natanz where Washington and Israel believe Iran has stored components of its nuclear programme.

The reported plans come as Trump faces mounting pressure to end the war with Iran, with negotiations stalled and the US president seeking a way to bring the conflict to a close without appearing to concede defeat.

No decision to deploy the bomb has been announced, and the White House has said Trump is keeping all options available.

Here is what to know about the weapon, its destructive capabilities and why the US is considering using it against Iran.

What is the 'mother of all bombs'?

The GBU-43/B Massive Ordnance Air Blast (MOAB) is the most powerful conventional bomb in the US military's arsenal.

Weighing approximately 9,800 kilograms (21,600 pounds) and measuring more than nine metres in length, the GPS-guided weapon was developed by the US Air Force in 2003 ahead of the American invasion of Iraq.

Unlike conventional bombs designed to penetrate fortified underground structures, the MOAB is an air-blast weapon that detonates above the ground, generating an enormous explosion across a wide area.

During testing in March 2003, the explosion produced a mushroom cloud visible from approximately 20 miles away.

The weapon was originally designed to destroy large concentrations of troops, military equipment and above-ground fortifications, although its potential targets later expanded to include caves and tunnels.

How destructive is the bomb?

The MOAB is capable of devastating large areas through an immense blast wave that can destroy buildings, military installations and other structures.

The weapon can devastate an area equivalent to approximately nine city blocks, according to the CNN report, although the actual extent of destruction depends on the terrain, surrounding structures and other conditions.

Despite its enormous size, the MOAB is not a nuclear weapon and does not produce the radioactive fallout associated with a nuclear explosion.

The bomb is GPS-guided and is delivered from a military transport aircraft rather than a conventional fighter jet. During its first combat deployment, it was dropped from an American MC-130 aircraft.

Its enormous size and destructive capabilities have also made it a tool of psychological warfare, with US military officials originally hoping that the threat of its use would intimidate enemy forces into surrendering.

Has the 'mother of all bombs' been used before?

Yes. The United States first deployed the MOAB in combat in April 2017, during Trump's first presidential term.

The bomb was dropped on a network of tunnels used by Islamic State (IS) militants in Afghanistan's eastern Nangarhar province, near the border with Pakistan.

The US military said the strike targeted underground tunnels and caves used by IS fighters to move between positions and launch attacks against Afghan and US forces.

Afghan officials reported that 36 IS fighters were killed and three underground tunnels destroyed, along with weapons and ammunition.

US and Afghan officials said at the time that no civilians were killed, although the strike attracted criticism over the use of such an enormous weapon.

Former Afghan President Hamid Karzai condemned the bombing, accusing Washington of using Afghanistan as a testing ground for destructive weapons.

Trump praised the operation at the time, describing it as "another successful job".

The 2017 strike remains the only publicly acknowledged combat use of the MOAB.

Why is Trump considering using it against Iran?

The reported plans come amid uncertainty over how Washington intends to end the conflict after more than six months of US military operations against Iran.

According to CNN, some Trump administration officials have discussed launching a final round of strikes before withdrawing American forces from the region, potentially allowing the president to present the operation as a military victory.

One source familiar with the plans said the proposed attacks could take place before a US military withdrawal from the region covered by Central Command.

The MOAB's psychological impact could also be a factor, with officials suggesting that its deployment could demonstrate overwhelming American military power and increase pressure on Tehran.

However, sources familiar with the discussions have questioned whether such an operation would achieve Washington's strategic objectives or bring the conflict any closer to an end.

Trump has publicly suggested he would refrain from additional military action before November's US midterm elections, although advisers reportedly remain uncertain whether he will maintain that position.

Could the bomb destroy Iran's underground nuclear facilities?

Military officials have expressed serious doubts about whether the MOAB could destroy Iran's most heavily fortified nuclear facilities.

Unlike specialised bunker-busting weapons, the MOAB is designed to unleash a massive explosion across the surface rather than penetrate deeply underground.

Pickaxe Mountain, for example, is believed to be protected by substantial layers of granite, potentially shielding its underground facilities from the bomb's effects.

The US possesses another weapon specifically designed for such targets: the GBU-57 Massive Ordnance Penetrator (MOP), which can penetrate hardened underground structures before detonating.

American B-2 bombers deployed 14 of these penetrator bombs during US strikes on Iranian nuclear facilities in June 2025, according to a US Department of Defense report.

The difference highlights a central question surrounding the reported plans: whether deploying the MOAB would inflict meaningful damage on Iran's nuclear programme or primarily serve as a show of force.

What would be the consequences of using it against Iran?

Deploying the MOAB against Iran would represent a significant escalation in the conflict, particularly if the weapon were used against energy infrastructure or facilities near populated areas.

Its enormous blast could cause widespread destruction, while damage to electricity supplies, industrial installations and other essential infrastructure could have consequences far beyond the immediate target.

The International Committee of the Red Cross has warned that explosive weapons with wide-area effects are particularly dangerous in populated areas because their impact can extend beyond intended military targets.

Such attacks can kill and injure civilians, destroy homes and disrupt services essential for survival, including water, electricity and healthcare.

The US military's use of the MOAB would also raise serious questions under international humanitarian law, which requires attacks to distinguish between military objectives and civilians, prohibits disproportionate civilian harm and obliges forces to take feasible precautions to protect civilians.