WASHINGTON _ The U.S. military dropped the most powerful non-nuclear bomb in its arsenal Thursday on a cave and tunnel complex that it said was used by Islamic State fighters in eastern Afghanistan.
The Pentagon's MOAB, or Massive Ordnance Air Blast, is a 30-foot-long, 21,600-pound munition that has been nicknamed the "mother of all bombs." It had never before been used in combat.
The military said the 11-ton bomb packed with more than 18,700 pounds of explosives was dropped at 7:32 p.m. as part of a U.S.-backed offensive on an Islamic State stronghold in Achin district in Nangarhar Province.
"The strike was designed to minimize the risk to Afghan and U.S. forces conducting clearing operations in the area while maximizing the destruction" to the militants, the statement said.
Army Gen. John W. Nicholson, commander of U.S. forces in Afghanistan, said the militants used bunkers and tunnels to "thicken their defense."
"This is the right munition to reduce these obstacles and maintain the momentum of our offensive," Nicholson said.
White House spokesman Sean Spicer said the massive bomb targeted tunnels and caves militants "used to move around freely, making it easier for them to target U.S. military advisers and Afghan forces in the area."
He said U.S. commanders "took all precautions necessary to prevent civilian casualties and collateral damage as a result of the operation."
Speaking by phone from Achin, Sher Nabi, a commander with the Afghan Local Police, said the bomb landed about a half-mile outside the town of Shogal, near the border with Pakistan.
Nabi, who leads a 60-man unit of a U.S.-backed militia supervised by the Afghan interior ministry, said Afghan security forces have carried out operations in the area for several days against suspected Islamic State supporters.
Nabi said the bomb killed "many militants" and destroyed their weapons. There were no immediate reports of civilian casualties.
Another U.S. munition, known the Massive Ordnance Penetrator, or MOP, is designed to penetrate hardened bunkers. It is even heavier than the MOAB but carries less explosive power.
The airstrike apparently was in the same area where Army Staff Sgt. Mark R. De Alencar, a 37-year-old Green Beret from Maryland, was killed Saturday after coming under fire.
He was the first American service member killed in combat this year in Afghanistan, and the 1,833rd since the U.S.-led invasion in late 2001.
The GBU-43 bomb was developed in 2002 to "put pressure on then-Iraqi dictator Saddam Hussein to cease and desist or the United States would not only have the means but use them against the unpopular tyrant," the Air Force said in 2005 news release.
The giant bomb was tested at Eglin Air Force Base in Florida in 2003, but was not used in Iraq.
On its final day of testing, March 11, 2003, a huge mushroom cloud could be seen from 20 miles away, the release said.
Earlier Thursday, the U.S. military announced an airstrike this week had accidentally killed 18 Syrian rebel fighters battling Islamic State alongside the international coalition in northern Syria.
