The US Navy reportedly used a new class of highly secret, non-nuclear electromagnetic pulse warheads during the opening hours of the Persian Gulf War to disrupt and destroy Iraqi electronics systems. The warheads converted the energy of a conventional explosion into a pulse of radio energy. The effect of the microwave attacks on Iraqi air defense and headquarters was difficult to determine because the effects of the HPM blasts were obscured by continuous jamming, the use of stealthy F-117 aircraft, and the destruction of Iraq's electrical grid. The warheads used during the Gulf War were experimental warheads, not standard weapons deployed with fielded forces.