Giant Bomb Was 'Right Weapon' For Attack On ISIS, U.S. General Says

"This was the right weapon against the right target," U.S. Army Gen. John W. Nicholson Jr. said, the morning after the U.S. dropped the most powerful non-nuclear bomb ever used in combat on an ISIS underground complex in Afghanistan.

The bomb was dropped in the Achin district of Nangarhar province in eastern Afghanistan. A video of the strike shows it hitting at the lower edge of a mountain, along a narrow valley, producing a huge shock wave and blast plume.

The nearly 22,000-pound bomb is believed to have killed at least 36 fighters and destroyed "large quantities" of weapons when it struck a network of tunnels, bunkers and other fortifications used by the offshoot group ISIS-K (for Khorasan province), according to an Afghan Defense Ministry spokesman.

The U.S. assessment is still in progress, a Pentagon official tells NPR's Tom Bowman, adding that there's a chance the death toll might include results from two other smaller operations against ISIS-K that took place Thursday night.

Nicholson said the "MOAB" ordnance — for Massive Ordnance Air Blast, or less formally, the "Mother of All Bombs" — was "designed to destroy caves and tunnels, which ISIS-K have been using, along with extensive belts of IEDs, to thicken their positions against our offensive."

U.S. special forces and Afghan commandos are now inspecting the site, Nicholson said, adding, "the weapon achieved its intended purpose."

Nicholson, the commander of the NATO-led Resolute Support force, discussed the operation Friday in a news conference in Kabul.

When he was asked about the timing of the unprecedented strike, and whether it had been influenced by the White House, Nicholson said, "In regard to timing, it's when we encountered this target on the battlefield."

The general said that because the spring offensive against ISIS-K had been slowed by fighters using caves and tunnels, "It was the right time to use it tactically, against the right target on the battlefield."

Addressing the Afghan public, Nicholson said all precautions were taken to prevent civilian casualties.

"We had persistent surveillance over the area before, during and after the operation, and now we have Afghan and U.S. forces on the site, and see no evidence of civilian casualties," Nicholson said. "Nor have there been any reports of civilian casualties.

After providing an update on the operation, Nicholson recounted a litany of offenses committed by ISIS-K, from beheadings and other public executions to suicide bombings.

The strike is part of a broader offensive, which Nicholson said is a sign of Afghanistan's commitment "to defeat Daesh in Afghanistan this year."

The official designation for the MOAB is the GBU-43/B; here's how NPR's Phil Ewing explains its origin:

"The GBU-43/B has been in the U.S. arsenal for more than 14 years, deployed to bases in the Middle East where it could be loaded aboard an American aircraft but never used until now. At more than 30 feet long, it's too big to fit inside the weapons bay of a standard Air Force bomber. Instead, troops load it into the cargo compartment of a specialized transport, the MC-130 Combat Talon, which releases it over the target by opening its ramp in the same way it might for paratroopers or air-dropped supplies. The bomb is guided by satellite to its target.

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