For a military with no formal allies or weapons suppliers, ISIS has an embarrassment of riches when it comes to military vehicles, with many of them pricey, newer model US-made vehicles that were given to Iraq at the end of the occupation, and promptly abandoned in the face of the ISIS offensive.

Kurdish Peshmerga Gen. Dedawa Khurshid, in his latest call for more foreign aid, reported that ISIS has so many US vehicles at this point that they are modifying many of them, including both armored military Humvees and bulldozers, to carry large caches of explosives, making them bombs on wheels.

Dubbed vehicle-borne explosive devices (VBEDs), the vehicles can carry massive amounts of explosives, and are often just driven headlong into the range of Kurdish and other forces and detonated by suicide bombers, causing mass casualties.

ISIS has a long history of using car bombs, but the use of these larger, armored vehicles allows them to deliver bigger explosive caches and drive straight into combat situations in ways that the traditional car bombs simply couldn’t. ISIS has used vehicle bombs as an effective morale killer for front-line troops on the other side, and reports have often credited such bombs with gains over Iraqi and Syrian ground troops.