Editing Chemical warfare (section)

===Delivery===
The most important factor in the effectiveness of chemical weapons is the efficiency of its delivery, or dissemination, to a target. The most common techniques include munitions (such as bombs, projectiles, warheads) that allow dissemination at a distance and spray tanks which disseminate from low-flying aircraft. Developments in the techniques of filling and storage of munitions have also been important.

Although there have been many advances in chemical weapon delivery since World War I, it is still difficult to achieve effective dispersion. The dissemination is highly dependent on atmospheric conditions because many chemical agents act in gaseous form. Thus, weather observations and forecasting are essential to optimize weapon delivery and reduce the risk of injuring friendly forces.{{citation needed|date=April 2017}}

====Dispersion====
[[File:Poison gas attack.jpg|thumb|upright=1.35|Dispersion of [[chlorine]] in [[World War I]]]]
Dispersion is placing the chemical agent upon or adjacent to a target immediately before dissemination, so that the material is most efficiently used.  Dispersion is the simplest technique of delivering an agent to its target. The most common techniques are munitions, bombs, projectiles, spray tanks and warheads.

World War I saw the earliest implementation of this technique. The actual first chemical ammunition was the French 26&nbsp;mm cartouche suffocante [[rifle grenade]], fired from a [[flare gun|flare carbine]]. It contained {{cvt|35|g|oz}} of the [[lachrymatory agent|tear-producer]] [[ethyl bromoacetate]], and was used in autumn 1914 – with little effect on the Germans.

The [[Military history of Germany|German military]] contrarily tried to increase the effect of {{cvt|10.5|cm|in}} [[shrapnel shell]]s by adding an irritant – [[dianisidine chlorosulfonate]]. Its use against the British at [[Battle of Neuve Chapelle|Neuve Chapelle]] in October 1914 went unnoticed by them. Hans Tappen, a chemist in the Heavy Artillery Department of the War Ministry, suggested to his brother, the Chief of the Operations Branch at German General Headquarters, the use of the tear-gases [[benzyl bromide]] or [[xylyl bromide]].

Shells were tested successfully at the Wahn artillery range near Cologne on January 9, 1915, and an order was placed for {{cvt|15|cm|in}} [[howitzer]] shells, designated 'T-shells' after Tappen. A shortage of shells limited the first use against the Russians at the [[Battle of Bolimów]] on January 31, 1915; the liquid failed to vaporize in the cold weather, and again the experiment went unnoticed by the Allies.

The first effective use were when the German forces at the [[Second Battle of Ypres]] simply opened cylinders of chlorine and allowed the wind to carry the gas across enemy lines. While simple, this technique had numerous disadvantages. Moving large numbers of heavy gas cylinders to the front-line positions from where the gas would be released was a lengthy and difficult logistical task.
[[File:Poison Gas Attack Germany and Russia 1916.JPG|thumb|Aerial photograph of a German gas attack on [[Russia]]n forces {{Circa|1916}}]]
Stockpiles of cylinders had to be stored at the front line, posing a great risk if hit by artillery shells. Gas delivery depended greatly on wind speed and direction. If the wind was fickle, as at the [[Battle of Loos]], the gas could blow back, causing [[friendly fire|friendly casualties]].

Gas clouds gave plenty of warning, allowing the enemy time to protect themselves, though many soldiers found the sight of a creeping gas cloud unnerving. This made the gas doubly effective, as, in addition to damaging the enemy physically, it also had a psychological effect on the intended victims.

Another disadvantage was that gas clouds had limited penetration, capable only of affecting the front-line trenches before dissipating. Although it produced limited results in World War I, this technique shows how simple chemical weapon dissemination ''can'' be.

Shortly after this "open canister" dissemination, French forces developed a technique for delivery of phosgene in a non-explosive artillery shell. This technique overcame many of the risks of dealing with gas in cylinders. First, gas shells were independent of the wind and increased the effective range of gas, making any target within reach of guns vulnerable. Second, gas shells could be delivered without warning, especially the clear, nearly odorless phosgene{{em dash}}there are numerous accounts of gas shells, landing with a "plop" rather than exploding, being initially dismissed as dud high explosive or shrapnel shells, giving the gas time to work before the soldiers were alerted and took precautions.

The major drawback of artillery delivery was the difficulty of achieving a killing concentration. Each shell had a small gas payload and an area would have to be subjected to [[saturation bombardment]] to produce a cloud to match cylinder delivery. A British solution to the problem was the [[Livens Projector]]. This was effectively a large-bore mortar, dug into the ground that used the gas cylinders themselves as projectiles – firing a {{cvt|14|kg|lb}} cylinder up to {{cvt|1500|m|ft|sigfig=1}}. This combined the gas volume of cylinders with the range of artillery.

Over the years, there were some refinements in this technique. In the 1950s and early 1960s, chemical artillery rockets and cluster bombs contained a multitude of submunitions, so that a large number of small clouds of the chemical agent would form directly on the target.

====Thermal dissemination====
[[File:Mc-1 gas bomb.png|thumb|An American-made [[MC-1]] gas bomb]]
Thermal dissemination is the use of explosives or [[pyrotechnic]]s to deliver chemical agents. This technique, developed in the 1920s, was a major improvement over earlier dispersal techniques, in that it allowed significant quantities of an agent to be disseminated over a considerable distance. Thermal dissemination remains the principal method of disseminating chemical agents today.

Most thermal dissemination devices consist of a bomb or projectile shell that contains a chemical agent and a central "burster" charge; when the burster detonates, the agent is expelled laterally.

Thermal dissemination devices, though common, are not particularly efficient. First, a percentage of the agent is lost by incineration in the initial blast and by being forced onto the ground. Second, the sizes of the particles vary greatly because explosive dissemination produces a mixture of liquid droplets of variable and difficult to control sizes.

The efficacy of thermal detonation is greatly limited by the flammability of some agents. For flammable aerosols, the cloud is sometimes totally or partially ignited by the disseminating explosion in a phenomenon called ''flashing''. Explosively disseminated VX will ignite roughly one third of the time. Despite a great deal of study, flashing is still not fully understood, and a solution to the problem would be a major technological advance.

Despite the limitations of central bursters, most nations use this method in the early stages of chemical weapon development, in part because standard munitions can be adapted to carry the agents.

[[File:Soviet chemical weapons canisters from a stockpile in Albania.jpg|thumb|left|Soviet chemical weapons canisters from a stockpile in Albania]]

====Aerodynamic dissemination====
Aerodynamic dissemination is the non-explosive delivery of a chemical agent from an aircraft, allowing aerodynamic stress to disseminate the agent. This technique is the most recent major development in chemical agent dissemination, originating in the mid-1960s.

This technique eliminates many of the limitations of thermal dissemination by eliminating the flashing effect and theoretically allowing precise control of particle size. In actuality, the altitude of dissemination, wind direction and velocity, and the direction and velocity of the aircraft greatly influence particle size. There are other drawbacks as well; ideal deployment requires precise knowledge of [[aerodynamics]] and [[fluid dynamics]], and because the agent must usually be dispersed within the [[boundary layer]] (less than {{cvt|200|-|300|ft|disp=or|m|order=flip|sigfig=1}} above the ground), it puts pilots at risk.

Significant research is still being applied toward this technique. For example, by modifying the properties of the liquid, its breakup when subjected to aerodynamic stress can be controlled and an idealized particle distribution achieved, even at [[supersonic speed]]. Additionally, advances in [[fluid dynamics]], [[computer model]]ing, and [[weather forecasting]] allow an ideal direction, speed, and altitude to be calculated, such that warfare agent of a predetermined particle size can predictably and reliably hit a target.