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 a cave complex believed to have Islamic State fighters according to the Associated Press.

White House spokesman Sean Spicer said in a daily briefing on Thursday that ISIS fighters use the caves to “move around freely.” He explained that in order to defeat the terrorist group, the U.S. must deny it operational space.

The press secretary declined to comment further on the bomb, referring requests to the Department of Defense.

President Donald Trump praised the U.S. military, calling the bombing a “very, very successful mission.”

“Everybody knows exactly what happened and what I do is I authorize my military. We have the greatest military in the world and they’ve done their job as usual. So, we have given them total authorization,” Trump said after meeting with first responders at the White House on Thursday.

The Pentagon said in a statement, “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 original goal of the MOAB was to act as a non-nuclear deterrent against Saddam Hussein, according to comments by former Defense Secretary Donald Rumsfeld to CNN and other reporters in 2003.

The bomb was then rapidly produced in-house at the Air Force Research Laboratory Munitions Directorate where it quickly made its way into the lab for prototype production, according to the Eglin Air Force Base.

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

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CNBC’s Christine Wang contributed to this report.

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