More than two-thirds of the High Mobility Multipurpose Wheeled Vehicles (HMMWV,) or Humvees, the U.S. supplied to Iraq to fight terrorists have ended up in the hands of Daesh terrorists.

And Daesh, has not wasted any time in converting those vehicles into one of its deadliest and most nightmarish tools: Vehicle-borne Improvised Explosive Devices (VBIED,) or suicide car bombs.

According to the Iraqi Prime Minister, Daesh controls about 2,300 armored U.S. HMMWVs. Most of those vehicles were seized after Daesh overran Mosul in June 2014.

In addition to being used in further attacks against Iraqi forces, these vehicles were sent over the border to Syria to help Daesh solidify its foothold there.

The HMMWVs were specifically created by the U.S. to be able to carry heavy loads and to sustain small-arms fire — qualities Daesh has found make the vehicles perfect for suicide bombings.

“There’s a simple reason the militants are using HMMWVs and other armored vehicles as rolling bombs,” Sean D. Naylor reports for Foreign Policy.