Smoke screen

Smoke screens are commonly deployed either by a canister (such as a grenade) or generated by a vehicle (such as a tank or a warship).

Whereas smoke screens were originally used to hide movement from enemies' line of sight, modern technology means that they are now also available in new forms; they can screen in the infrared as well as visible spectrum of light to prevent detection by infrared sensors or viewers, and they are also available for vehicles in a super-dense form used to block laser beams of enemy laser designators or rangefinders.

They are much slower to respond than pyrotechnic sources, and require a valuable piece of equipment to be sited at the point of emission of the smoke.

To overcome this latter problem, they may be used in fixed posts widely dispersed over the battlefield, or else mounted on specially adapted vehicles.

Many armoured fighting vehicles can create smoke screens in a similar way, generally by injecting diesel fuel onto the hot exhaust.

Warships have sometimes used a simple variation of the smoke generator, by injecting fuel oil directly into the funnel, where it evaporates into a white cloud.

[1][2] The proliferation of thermal imaging FLIR systems on the battlefields necessitates the use of obscurant smokes that are effectively opaque in the infrared part of electromagnetic spectrum.

Other materials used as visible/infrared obscurants are micro-pulverized flakes of brass or graphite, particles of titanium dioxide, or terephthalic acid.

Older systems for production of infrared smoke work as generators of aerosol of dust with controlled particle size.

Damage of the lower airways can manifest itself later as well, due to fine particles of zinc chloride and traces of phosgene.

Symptoms include dyspnea, retrosternal pain, hoarseness, stridor, lachrymation, cough, expectoration, and in some cases haemoptysis.

When chlorosulfuric acid comes in contact with water, a strong exothermic reaction scatters the corrosive mixture in all directions.

In contact with damp air it hydrolyzes readily, resulting in a dense white smoke consisting of droplets of hydrochloric acid and particles of titanium oxychloride.

Red phosphorus is less reactive, does not ignite spontaneously, and its smoke does not cause thermal burns - for this reason it is safer to handle, but cannot be used so easily as an incendiary.

While very effective in the visible spectrum, cool phosphorus smoke has only low absorption and scattering in infrared wavelengths.

Early smoke screen experiments attempted the use of colored pigment, but found that titanium dioxide was the most light scattering particle known and therefore best for use in obscuring troops and naval vessels.

in the wars of ancient India, where incendiary devices and toxic fumes caused people to fall asleep.

[8] It was later recorded by a Greek historian, Thucydides, who described that the smoke created by the burning of sulphur, wood and pitch was carried by the wind into Plataea (428 B.C.)

[10] Later, between 1790 and 1810, Thomas Cochrane, 10th Earl of Dundonald (1775–1860), a Scottish Naval commander and officer in the Royal Navy who fought during the French Revolutionary and Napoleonic Wars, devised a smoke screen created through the burning of sulphur which would be used in warfare after learning about the same methods used at Delium and Plataea.

[14][15][16] A toxic variant of the smokescreen was used and devised by Frank Arthur Brock who used it during the Zeebrugge Raid on 23 April 1918, the British Royal Navy's attempt to neutralize the key Belgian port of Bruges-Zeebrugge.

For the crossing of the Dnieper river in October 1943, the Red Army laid a smoke screen 30 kilometres (19 mi) long.

At the Anzio beachhead in 1944, US Chemical Corps troops maintained a 25 km (16 mi) "light haze" smokescreen around the harbour throughout daylight hours, for two months.

In the Vietnam War, "Smoke Ships" were introduced as part of a new Air Mobile Concept to protect crew and man on the ground from small arms fire.

It is not until the early twentieth century that there is clear evidence of deliberate use of large scale naval smokescreens as a major tactic.