Afghanistan/US, ‘Mother of all bombs’

Introductory Text
In the context of the so-called war against terrorism, the US military dropped its most powerful non-nuclear bomb over Afghanistan in April 2017. Although the attack did not cause damage as widespread as initially expected and reported, the use of this powerful fuel-air bomb sparked controversy over why its use was necessary in this particular case.
Case prepared by Ms. Laura Tribess, student at the University of Geneva (Switzerland) and the University of Freiburg (Germany), under the supervision of Professor Marco Sassòli and Mr. George Dvaladze, teaching and research assistant, both at the University of Geneva.

N.B. As per the disclaimer, neither the ICRC nor the authors can be identified with the opinions expressed in the Cases and Documents. Some cases even come to solutions that clearly violate IHL. They are nevertheless worthy of discussion, if only to raise a challenge to display more humanity in armed conflicts. Similarly, in some of the texts used in the case studies, the facts may not always be proven; nevertheless, they have been selected because they highlight interesting IHL issues and are thus published for didactic purposes.


A. U.S. Bombs, Destroys Khorasan Group Stronghold in Afghanistan

[Source: US, Department of Defense, Press release, “U.S. Bombs, Destroys Khorasan Group Stronghold in Afghanistan”, 13 April 2017, available at

KABUL, Afghanistan – At 7:32 p.m. local time today, U.S. Forces Afghanistan conducted a strike on an Islamic State of Iraq and Syria-Khorasan tunnel complex in Achin district, Nangarhar province, Afghanistan, as part of ongoing efforts to defeat ISIS-K in Afghanistan […].

ISIS-K, also known as the Khorasan group, is based in the Afghanistan-Pakistan region and is composed primarily of former members of Tehrik-e Taliban Pakistan and the Afghan Taliban.

The strike used a GBU-43/B Massive Ordnance Air Blast bomb dropped from a U.S. aircraft. The strike was designed to minimize the risk to Afghan and U.S. forces conducting clearing operations in the area while maximizing the destruction of ISIS-K fighters and facilities.

“As ISIS-K’s losses have mounted, they are using [improvised bombs], bunkers and tunnels to thicken their defense,” said Army Gen. John W. Nicholson, commander of U.S. Forces Afghanistan. “This is the right munition to reduce these obstacles and maintain the momentum of our offensive against ISIS-K.”

U.S. forces took every precaution to avoid civilian casualties with this strike and will continue offensive operations until ISIS-K is destroyed in Afghanistan.


B. US military defends dropping 'mother of all bombs' on ISIS in Afghanistan

[Source: “US military defends dropping 'mother of all bombs' on ISIS in Afghanistan”, James Griffiths, Barbara Starr and Angela Dewan, CNN, 14 April 2017, available at]

(CNN) – The US military on Friday defended its decision to drop its most powerful non-nuclear bomb on ISIS positions in Afghanistan, describing it as a “tactical” move.


The strike in Nangarhar province near the Pakistan border killed 36 ISIS fighters, Afghan officials said. The US military previously estimated ISIS had 600 to 800 active fighters in the area but was unclear whether it had hoped to strike more.

The blast destroyed three underground tunnels as well as weapons and ammunition, but no civilians were hurt, Afghan and US officials said.

However, ISIS denied that any of its fighters were killed or injured, according to a statement in Arabic distributed by the terror group's media wing, Amaq News Agency.

The US military was quizzed Friday on whether the 21,600-pound behemoth, known as the “mother of all bombs” for its extraordinary force, was necessary for that particular target.

The GPS-guided bomb is capable of destroying an area equivalent to nine city blocks.

“This was the right weapon against the right target,” Gen. John Nicholson, commander for US forces in Afghanistan, told a press conference.


The general confirmed the strike was carried out in coordination with Afghan officials and said rigorous surveillance had been conducted to prevent any civilian deaths.


Afghan President Ashraf Ghani said he approved of the strike and that it was designed to support Afghan and US forces conducting clearance operations in the region.



C. What is the ‘Mother of All Bombs’ that the U.S. Dropped on Afghanistan?

[Source: “What is the ‘Mother of All Bombs’ That the U.S. Just Dropped on Afghanistan”, Larry Greenemeier, Scientific American, 13 April 2017, available at]

The idea of dropping an air-blast bomb – even if it’s the largest nonnuclear ordnance ever used by the U.S. in combat – to target fighters holed up in tunnels deep underground might at first seem counterintuitive. The GBU-43/B Massive Ordnance Air Blast Bomb, or "Mother of All Bombs" (MOAB), which the Air Force unleashed on ISIS fighters and tunnels Thursday in […] Afghanistan’s Nangarhar Province, never actually struck the ground. But the massive crunch of air pressure created by the nearly 22,000-pound MOAB would have wiped out anyone in the vicinity, and certainly sent a clear signal that the Trump administration is willing to use unprecedented force.

Unlike a bomb designed to actually penetrate a building or the ground, the MOAB (also called a fuel-air bomb) has a “proximity fuse” on its nose that ignites the warhead when it reaches a certain altitude—which might be anywhere between 50 and 1,000 feet—says Edward Priest, a former Air Force Special Operations combat controller […]. “When they blow up, they blast fuel into the air,” Priest explains. “That fuel atomizes. Then there’s a secondary explosion that lights the fuel that’s been atomized.”

An air blast bomb “doesn’t throw out a lot of fragmentation like you’d expect from a normal bomb—it’s all blast overpressure, which can blow down trees and use the trees themselves as the fragmentation,” Priest says. “That type of bomb wouldn’t work well, for example, to destroy tanks, although the overpressure would kill the people in them. You’d overpressure the people hiding in the caves there. You’d never find them—it just blows your lungs out of your mouth. It kind of turns you inside out.”

The use of air-blast bombs in Afghanistan dates back to the beginning of the U.S. military’s arrival following the 9/11 attacks on New York City and Washington, D.C. […] Use of the BLU-82—aka the "Daisy Cutter"—was phased out in subsequent years. “This is a tough munition to use,” says A. J. Clark, a former military intelligence analyst […]. “It might make sense if there’s a concentration of enemy troops but it’s not something you want to use when you have friendlies or civilians in the vicinity. There’s no way to control it.”

The decision to use the MOAB at this time was probably as much political as it was strategic. “More than anything, anytime you drop one of these you want to make an audacious statement, in this case to reinforce our resolve to fight in Afghanistan,” Priest says, adding they produce a large mushroom cloud that can be seen for miles.

Clark agrees. “These types of bombs were developed as much for their psychological impact as anything else,” he says. […] After reaching an impasse in Afghanistan for the past five years, he thinks the Nangarhar bombing says “we’re taking things to a new level in Afghanistan.”



I. Classification of the Situation and Applicable Law

1.     Considering that the US operated in Afghanistan on the request of the Afghan government, how would you classify the situation in Afghanistan in 2017? Was there an armed conflict? If yes, who were the parties to it? Was ISIS a party to that conflict? What additional information, if any, would you need to make such a determination? What law is applicable to the US in Afghanistan? (GC I-IV, Art. 3)

II. Means of Warfare

2.     (Document C)Does IHL provide for specific rules regarding certain weapons? Which weapons are explicitly prohibited? Why are they prohibited? Which weapons are subject to additional restraints? Are those rules the same for IACs and for NIACs? Do fuel-air bombs such as the one used by the US in Afghanistan fall under any of those prohibitions or additional restraints? (1980 Convention on Prohibitions or Restrictions on the Use of Certain Conventional Weapons; 2001 Amendment to the 1980 Convention; Protocols I, II, III, IV, V to the 1980 Convention; Convention on Cluster Munition1925 Geneva Chemical Weapons Protocol; 1993 Convention on Chemical Weapons; 1972 Convention on Biological Weapons; CIHL, Rules 7286)

3.     Does IHL set limits to the use of means of warfare? Even when exclusively targeting legitimate targets with means that are not specifically prohibited? What principles are applicable? Are those principles the same under IHL of IACs and of NIACs? (P I, Arts 35, 51 (4); CIHL, Rules 70, 71)

4.     (Document C) How do you determine whether a weapon causes superfluous injury or unnecessary suffering? Are the described effects of the fuel-air bomb used by the US of such a nature? Why, or why not? (P I, Art. 51 (4); CIHL, Rule 70)

5.     (Document C) What does the prohibition of indiscriminate means and methods of warfare entail? How do you determine whether a weapon is inherently indiscriminate? In your opinion and considering the described effects of the bomb, is the fuel-air bomb used by the US inherently indiscriminate? Can it be directed at the specific military objective? (P I, Art. 51 (4); CIHL, Rules 12, 71)

6.     (Documents A, B and C) In the conduct of hostilities, what principles and rules limit the use of a weapon in an attack?

a.     What is the principle of proportionality under IHL? Does it mean that a weapon as such must be proportionate to the target? Is it admissible to use a weapon that is larger than necessary to meet the objectives of an attack in order to make a “statement”? Think of damage to civilian objects in the vicinity, or possible environmental damage. Could the psychological impact of a weapon be counted as a military advantage gained from the attack? What if the attacker believes that the psychological impact of the use of that weapon will bring the conflict to a quicker end? Or does it not have any legal relevance? Even if there is no collateral damage? (P I, Art. 51 (5) (b); CIHL, Rule 14)

b.     What are the obligations of a party to a conflict regarding precautions in attack? Did the US have to take precautionary measures in this case? For the benefit of whom? How do you determine the feasibility of precautions? Can you give examples of precautionary measures the US could and should have taken in the present case? Could precaution warrant the choice of a weapon with a smaller range or effects radius? (P I, Art. 57 (2); CIHL, Rules 1521)