White phosphorus (weapon)

NFPA 704 "fire diamond"
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White phosphorus is a material made from a common allotrope of the chemical element phosphorus that is used in smoke, tracer, illumination, and incendiary munitions. Other common names include WP and the slang term "Willie Pete" or "Willie Peter" derived from William Peter, the World War II phonetic alphabet for "WP", which is dated from its use in World War II and Vietnam and is still sometimes used in military jargon. As an incendiary weapon, white phosphorus burns fiercely and can ignite cloth, fuel, ammunition, and other combustibles.

In addition to its offensive capabilities, white phosphorus is a highly efficient smoke-producing agent, which burns quickly and produces an immediate blanket of smoke. As a result, smoke-producing white phosphorus munitions are very common, particularly as smoke grenades for infantry, loaded in grenade launchers on tanks and other armored vehicles, or as part of the ammunition allotment for artillery or mortars. These create smoke screens to mask from the enemy movement, position, infrared signatures, or the origin of fire.

White phosphorus is believed to have been first used by Fenian arsonists in the 19th century, in the form of a solution in carbon disulfide. When the carbon disulfide evaporated, the phosphorus would burst into flames. This mixture was known as "Fenian fire" and allegedly was used by disgruntled itinerant workers in Australia to cause delayed destruction of shabby sleeping quarters.

In 1916, during an intense struggle over conscription for the First World War, 12 members of the Industrial Workers of the World, a workers union opposed to conscription, were arrested and convicted for using or plotting to use incendiary materials, including phosphorus. It is believed that eight or nine men in this group, known as the Sydney Twelve, had been framed by the police. Most were released in 1920 after an inquiry.

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