WASHINGTON — The United States dropped the “mother of all bombs” — the largest conventional bomb in the American arsenal — on an Islamic State cave complex in Afghanistan on Thursday, the Pentagon said, unleashing a munition so massive that it had to be dropped from the rear of a cargo plane.
The bomb, officially called the GBU-43/B Massive Ordnance Air Blast — hence its moniker — hit a tunnel complex in the Achin district of Nangarhar Province, according to a statement from the United States military in Afghanistan. It did not say how many militants were killed.
During the years of intense fighting in Afghanistan, a handful of similar bombs were used by the United States to destroy caves believed to be used by forces of the Taliban and Al Qaeda, as well as to frighten troops dug into trenches who were not immediately killed by the weapon. That the United States is again using this type of ordnance reflects the changing nature of the foe in Afghanistan, and the fact that the Islamic State, like the Taliban and Al Qaeda, is now also using caves and tunnels.
Thursday’s strike was the first combat use of GBU-43/B, which is an updated version of the older bombs, said Adam Stump, a Pentagon spokesman.
Islamic State fighters in Afghanistan “are using I.E.D.s, bunkers and tunnels to thicken their defense,” Gen. John W. Nicholson, the United States commander in Afghanistan, said, referring to improvised explosive devices, in the statement announcing the strike.
“This is the right munition to reduce these obstacles and maintain the momentum of our offensive against ISIS-K,” he added, using another name for the Islamic State in Afghanistan.
It was unclear whether any civilians were killed. The military insisted that it took every precaution to avoid such casualties. But the Pentagon has come under increasing criticism that as it has intensified the fight against the Islamic State in Iraq and Syria, the civilian death toll has risen sharply.
Sean Spicer, the White House spokesman, addressed the bombing during his Thursday briefing, saying, “We must deny them operational space, which we did,” referring to the Islamic State in Afghanistan.
The bomb was dropped from an MC-130, a cargo plane with a rear door.