The United States military has dropped its biggest non-nuclear bomb, a 21,000-pound GBU-43B bomb in the Nangarhar Province in eastern Afghanistan and near the Pakistani border.

The bombed area is known to be populated by ISIS militants according to military analysts, and the bombing came just a few days after an American Green Beret was killed in the area by alleged ISIS fighters.

No word yet on casualties.

The bomb, also known as MAOB (Massive Ordinance Air Blast) or the “Mother Of All Bombs, was first tested in 2003 and has never been used before in combat.