How has white phosphorus been used to generate military smoke?

White phosphorus is used for military purposes primarily as a source of smoke and as a filling for incendiary shells and grenades. Its effectiveness in generating smoke stems from its high chemical reactivity; when exposed to air, white phosphorus spontaneously ignites at approximately 35 °C (95 °F).1

Upon combustion, it reacts vigorously with oxygen to produce dense clouds of phosphorus oxides, which effectively obscure visibility on the battlefield. Because of its extreme reactivity and tendency to inflame in air, white phosphorus must be stored under water or another inert liquid to prevent accidental ignition.1