Beginning in July 2003, the Iraqi insurgency used IEDs to target invading coalition vehicles. Many of these IEDs were made from military explosives looted from munitions bunkers following the 2003 invasion, such as landmines stripped of their explosives, 155-millimetre artillery shells rigged with blasting caps and modified aviation bombs of 500 lb or more, detonated by systems such as pull-wires and mechanical detonators, cell-phones, garage-door openers, cables, radio control (RC), and infrared lasers among others. To counter increasing armor protection, the insurgents have also developed IEDs that make use of explosively formed projectiles (EFPs); these are essentially cylindrical shaped charges usually constructed with a machined concave metal disc (often copper) facing the target, pointed inward. The force of the shaped charge turns the disc into a high velocity slug, capable of penetrating the armor of most enemy vehicles. Commonly positions for IEDs include on utility poles, road signs or trees, buried underground or in piles of garbage, disguised as rocks or bricks, and even inside dead animals. Typically they explode underneath or to the side of the vehicle, however, IEDs in elevated positions such as on road signs are able hit less protected areas. It has been estimated by the "Washington Post" that as much as 64% of U.S. deaths in Iraq occurred due to IEDs.