When the US dropped a 22,600-pound bomb near suspected ISIS tunnels in Afghanistan’s Nangarhar province on Thursday, the blast from the explosion would have rushed into the furthest reaches of the mountain complex about a mile away. The GBU-43, known as Moab—short for Massive Ordnance Air Blast, or, colloquially, Mother of All Bombs—is the largest non-nuclear, non-penetrating bomb in the US arsenal. And until now, this mother had never been used outside of a testing facility.
US Central Command confirmed Thursday that it dropped the Moab on tunnels it suspected ISIS-Khorsan, the local ISIS group, of inhabiting. “As ISIS-K’s losses have mounted, they are using IEDs, bunkers, and tunnels to thicken their defense. This is the right munition to reduce these obstacles,” said General John W Nicholson, who commands US forces in Afghanistan.
Though this is the first time the Moab has ever been used, it’s been around since 2002. So why did it take the United States 15 years to drop it? It’s not the size. It’s because Moab’s highly specialized impact means that the US government didn’t have an appropriate target for it until today.
‘Just a Big Canister’
In 2002, the Air Force Research Laboratory designed the Moab for possible use in the Iraq War, and ordered the McAlester Army Ammunition Plant in Oklahoma to make around a dozen, according to Mark Cancian, Senior Advisor at the Center for Strategic and International Studies. That limited run was due not to an exorbitant cost (they take millions to make, but that’s due to size, not sophistication), but rather the narrow use case for the bomb itself. A year later, the government tested the Moab in Florida for the first time.
“The Moab is not a particularly sophisticated weapon,” says Cancian. “It is really just a big canister with a lot of explosive in it.” In fact, Moab derives its uniqueness from that ratio of explosive-to-other-material: Aside from its casing, it’s almost entirely composed of H6 explosive material—a highly stable mixture that makes it safe to store a bomb this big without worrying it will inadvertently explode and take an army base with it.
In trying to understand what makes the Moab different, it’s helpful to understand what it isn’t. Aside from not being a nuclear weapon, it’s also not a penetrator or “bunker buster,” meant to burrow deep into the ground. Rather, it’s a concussive bomb designed to explode above ground and create a massive blast. Most conventional bombs—like the J-dams the US regularly drops on Syria, Iraq, and Afghanistan—will be some small percentage of explosive, and a much larger part casement that will kill people by bursting apart into a thousand pieces. The Moab takes the inverse approach.
Its objective? Create a blast big enough to reach deep into areas that other conventional bombs can’t. The Moab also differs from its Russian cousin, known as the Father of All Bombs, a weapon that’s both bigger than the Moab and thermobaric, meaning it uses gas to create a huge fireball.
“The Moab is just a shock wave,” says Cancian. A shock wave so big that it would cover 150 meters.
Generating a wave that big requires a bomb that’s proportionally massive. It weighs over 11 tons, and has to be hauled by a cargo plane, and dropped directly above its target. It floats to the ground with a parachute, and explodes just before impact. Odd-looking fins ring its tail, though they’re decidedly not aerodynamic. Instead, they slow the bomb down as it falls from the plane. This is to buy people in the plane enough time to get away.
“If it blows up too quickly, it’ll take the aircraft down with it,” says Cancian.
The Moab has been a known part of the US arsenal—and was even at one point suggested as a solution to the Gulf oil spill—but its nearly two-decade dormancy to this point has a surprisingly straightforward explanation.
“It’s a particular type of bomb best for a particular type of target. So you need that match,” says military expert and author Peter Singer. From what the government has revealed about today’s mission, Singer says that match fit.
‘Drop something like this in Mosul, you’d level half the city.’ Mark Cancian, CSIS
J-Dams won’t work to get into deep tunnels, because the fragmentary material they shoot out stops at the first twist the tunnel takes. To avoid them, combatants just need to go deeper into the tunnel. Bombs designed specifically to penetrate underground pose similar problems. Though effective when targeting individual below-ground targets, they struggle with crippling long, winding networks. That’s where a massive concussive bomb has the advantage: Its blast can turn corners, and push all the way to the furthest reaches of a cave.
“We made Moab for this kind of target,” says Cancian. “My guess is that we just didn’t know where these tunnels were before.”
Deploying the Moab in nearly any other situation also presents some insurmountable drawbacks. Its sheer size means only certain aircraft can deploy it. Plus its large blast range makes it inefficient for targeted mission. But by far the biggest impediment to using it more often is the risk to civilian life.
“These caves I’m assuming are out in the mountains, in a very uninhabited spot, so you’re not as worried about civilians. But to drop something like this in Mosul, you’d level half the city,” says Cancian. That kind of fallout likely explains why the Moab sat out the heaviest fighting of the Iraq war.
It’s important to remember that today’s mission has garnered attention not because it represents a ramp up in the fight against ISIS, but because it involves a really, very big bomb.
“Is it all that much different from having a B-1 come in and just saturate the area with 12 1,000-pound bombs? I don’t think so,” said one national security official who declined to be named. “We’ve been dropping bombs in Afghanistan for 15 years now. Does the size really matter?”
In fact, just last week the US dropped a combined 59,000 tons of explosives on a single Syrian airbase. It’s not a direct comparison, of course, given the nature of the strikes. But it underscores that the US uses mass quantities of explosives on a regular basis, whether that comes in the form of a single Moab or a few dozen Tomahawks. In fact, the US has used massive concussive bombs before; during Vietnam, US forces dropped a 15,000 pound predecessor to the Moab known as a Daisy Cutter. It even used one in 2001, to clear out a Taliban tunnel network.
This time, the Moab served its best strategic purpose—though that may extend beyond the actual impact. Dropping the mother of all bombs also sends a message. “To the Taliban that there’s a new sheriff in town,” says the national security official. Presumably also to ISIS, North Korea, and Iran. And the fact that it’s such a big blast doesn’t hurt for courting media attention that helps deliver that warning.
“Most generally, use of a bomb of this size now is probably a broad warning to others to avoid brinksmanship with the United States,” says Rebecca Zimmerman, a policy researcher at RAND.
“You…wouldn’t cover the story if this was 10 J-Dams, same mission different bombs,” says Singer. The Moab, though, makes an impact.