A report by The Wall Street Journal last week revealed a secretive U.S. military weapon designed explicitly to reduce civilian casualties in targeted strikes. Unlike a traditional Hellfire missile dispatched from an aerial drone, the missile variant packs no payload, no explosive. The catch? It drops 100 pounds of metal on a target, shredding them to pieces with six giant knives.

As the WSJ reports, the weapon, developed under the Obama administration, is only deployed in special circumstances. Known as the R9X, it is specifically designed for precision operations in which a normal explosive Hellfire missile would result in civilian deaths.

The paper was able to confirm two operations that employed the R9X: one this January by the Department of Defense that killed Jamal al-Badawi; and another that took place in Syria two years ago, resulting in the death of Al Qaeda leader Ahmad Hasan Abu Khayr al-Masri.

The weapon, nicknamed the “ninja bomb,” wouldn’t be the first time the U.S. military has relied on the remarkably deadly combination of metal and gravity. In both Korea and Vietnam, the U.S. military deployed so-called “Lazy Dog” bombs — two-inch metal projectiles that rained down from the sky by the hundreds, picking up speed before making deadly impact.

While the effect was often grisly, the bombs left no unexploded material behind — a perk (if you can call it that) not unlike the grim benefit of minimizing civilian casualties by dropping 100 pounds of sharp metal onto the heads of your enemies.