The U.S. military on Thursday dropped one of its most powerful bombs — a massive 21,000-pound munition nicknamed the “Mother of All Bombs” — on an Islamic State tunnel complex in Afghanistan, the first time it has been used in combat.

The GBU-43, or massive ordnance air blast weapon, was dropped from a U.S. aircraft in Nangahar province, where U.S.-backed Afghan forces are battling the Islamic State, also known as ISIS.

President Trump has pledged to ramp up the pressure on ISIS and has given his battlefield commanders more leeway to make combat decisions.

Critics of President Obama, such as Republican Sen. John McCain, chairman of the Armed Services Committee, said Obama “micromanaged” military decisions from the White House, such as placing strict limits on troop numbers.

“We have given them total authorization,” Trump said of the military.

“This was another very, very successful mission,” Trump said of the bombing.

A GBU-43 would not only destroy a tunnel complex, it would also have a psychological impact on the militants because of its destructive power. The blast can be heard for miles and is very different from the small munitions the military uses when trying to hit a small target and minimize surrounding damage.

“The United States takes the fight against ISIS very seriously and in order to defeat the group we must deny them operational space, which we did,” White House spokesman Sean Spicer said.

Fighting between ISIS and Afghan forces in the region has intensified recently. A U.S. Special Forces soldier advising the Afghans was killed in the area Saturday, the first U.S. combat death this year.

The Islamic State has emerged over the past year as a threat in Afghanistan, though the organization is not nearly as large as the Taliban, which ruled the country until the U.S.-led invasion in 2001.

The U.S. military likely chose to use the bomb, which cost about $16 million each, because the tunnel complex was in a remote area where there was little danger of civilian casualties.

“This is the right munition to reduce these obstacles and maintain the momentum of our offensive against (the Islamic State),” Gen. John Nicholson, the commander of U.S. forces in Afghanistan said in statement.

The bomb explodes in the air, creating air pressure that can collapse tunnels and buildings. It was designed to be dropped from a C-130, a cargo plane that is also used to airdrop supplies.

“U.S. forces took every precaution to avoid civilian casualties with this strike,” the military said in a statement.