For defense purposes, the military has an ongoing interest in reliably detecting the firing of small arms weapons and the launching of larger weapons such as rocket propelled grenades (RPGs), mortars, tanks, artillery, rockets, and missiles. Optical, Infrared (IR), and acoustic sensors exist today that can detect these weapons. However, these detection methods have not always proven reliable and do not work as well during obscured environmental conditions caused clouds, fog, dust, and rain. Passive Radio Frequency (RF) detection of these weapons could provide a benefit over other methods by providing fast detection through obscured environments over extended ranges. Since 2003, we have developed and deployed sensors capable of recording and analyzing RF emissions acquired during small arms gunfire and during the launching of the larger weapons. The basic phenomenology depends on the type of weapon, but we have shown that RF detection of these events is possible.