The Pentagon said U.S. military forces dropped the largest non-nuclear bomb in Afghanistan on Thursday.

This is the first time the GBU-43 bomb, known as the “mother of all bombs,” has ever been used in combat, according to Adam Stump, the Pentagon spokesman. The bomb contains 11 tons of explosives and is formally known as the Massive Ordnance Air Blast (MOAB) bomb.

“As ISIS-K’s losses have mounted, they are using IEDs, bunkers and tunnels to thicken their defense,” General John W. Nicholson, commander of U.S. forces in Afghanistan, said in a statement. “This is the right munition to reduce these obstacles and maintain the momentum of our offensive against ISIS-K.”

Stump says the bomb was dropped on cave complex believed to have Islamic State fighters according to the Associated Press.

The Pentagon said, “U.S. forces took every precaution to avoid civilian casualties with this strike. U.S. forces will continue offensive operations until ISIS-K is destroyed in Afghanistan.”

The bomb was rapidly produced in-house at the Air Force Research Laboratory Munitions Directorate, according to the Eglin Air Force Base. The base said the MOAB started out as an idea before quickly making its way into the lab for prototype production.

This story is developing. Please check back for further updates.

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