U.S. forces used their largest non-nuclear bomb for the first time in combat on Thursday, striking Islamic State militants in Afghanistan’s Nangarhar province around 7:30 p.m. local time.

The strike was carried out “as part of ongoing efforts to defeat ISIS-K in Afghanistan in 2017,” according to a U.S. Central Command press release.

The military objective was to drop the bomb “and get it over and done with and get the ISIS forces killed off,” Barbara Starr, CNN’s Pentagon correspondent, said.

The bomb used is a GBU-43 or Massive Ordnance Air Blast, commonly referred to as the “mother of all bombs.” It contains 11 tons of explosives, according to The Associated Press.

It was chosen in an effort to “minimize the risk to Afghan and U.S. Forces conducting clearing operations in the area while maximizing the destruction of ISIS-K fighters and facilities,” the CENTCOM press release says.

“As ISIS-K’s losses have mounted, they are using IEDs, bunkers and tunnels to thicken their defense,” Gen. John W. Nicholson, commander of the U.S. forces in Afghanistan, said in the release.

A specialized weapon was required to strike such an unusual target, Mark Cancian, senior adviser to the Center for Strategic and International Studies’ international security program, told The WorldPost.

“Presuming that this is a deep tunnel, you need something that has enough concussion to go deep into the tunnel,” he said.

The timing of the strike suggests that U.S. forces may have only recently discovered the tunnel, Cancian said, possibly thanks to eyes on the ground. But the strike would have nevertheless sent a message to Islamic State militants that “there’s no safe place, no matter how deep of a tunnel you dig.”

Efforts to dismantle ISIS strongholds have been concentrated in Iraq and Syria. But a small stronghold of fighters made up of former Taliban members has grown in eastern Afghanistan since 2014. The group is known as Islamic State Khorasan, according to a U.S. Institute for Peace report released in November.

“IS-K receives funding from the Islamic State’s Central Command and is in contact with leadership in Iraq and Syria, but the setup and day-to-day operations of the Khorasan province have been less closely controlled than other Islamic State branches such as that in Libya,” the report notes.

President Donald Trump lauded the strike on Thursday, calling it “another very, very successful mission.” Just last week, he also approved a strike on a Syrian air base in the aftermath of a chemical weapon attack on Syrian civilians that killed almost 100 people.

Trump, while advocating for a lessened U.S. role in international conflicts, also claimed he would “bomb the shit” out of the Islamic State during his presidential campaign.

This story has been updated with remarks from Cancian and Trump.