Ypres, 22 avril 1915 : les premières attaques au gaz de combat

the first gas attacks in combat The military use of toxic products has been well known since the Middle Ages: asphyxiating fumes used on Huguenot caves in the Dauphiné province and chemicals distilled by the Italian scientist L. Fioravanti de Bononia.

The background history of gas in combat It was therefore at the beginning of the 19th Century that the first chemical weapons appeared. In 1813, on the advice of a Berlin chemist, instead of bayonets, Von Bulow used brushes soaked in "prussic" acid, when his men mounted an attack on Napoleon's men. In 1830 a French chemist, Efortier, invented an asphyxiating incendiary bomb. In 1845, General Pelissier used toxic gases against the Kabylian Ouled Riah tribe. In 1854, the British developed a toxic bomb, filled with a derivative of arsenic. In 1887, A. von Bayer discovered tear-gas in his laboratory in Munich. Lastly, in 1904-1905 during the Russo-Japanese war, if we are to believe the health department, toxic gases were used on both sides. Rapid progress in science and technology and in chemistry in particular pushed the industrialised nations towards extending their areas of research into new weapons, all the more so since a conflict between the great powers still remained a possibility. This development was such that the Hague Convention of the 18th October 1907 decided to uphold articles 23a and 23e drafted during the first conference of the 28th July 1899. Article 23a prohibited the use of poison or poisoned weapons and condemned the use of such products in contaminating water and food etc. Article 23e proscribed the use of any weapons and projectiles or substances likely to cause unnecessary suffering.

The principal types of toxic agents used during the Great War Chemical agents were classed in 3 general categories according to their use: [list]Irritants: they attack the eyes, nose and throat, reducing the opponent's ability to fight, whilst not causing death. The best known are: Benzyl Bromide, known in France under the name of Cyclite and Xylyl bromide (obus T to the Germans) - these are colourless refractive liquids with quite a pleasant aromatic odour; monobromoacetone and monobromo methylethylketone, both pale yellow in colour in their liquid state, they are both toxic and lachrymatory and were used in the "1" green cross artillery shell in France; monobromoacetone was used under the name of Martonite. [list]Suffocating chemicals: they generally have an immediate effect causing serious lesions on the human body and can lead to death. The best known of these gases is Chlorine which was used during the first major German attacks of the spring of 1915. Two other toxic agents were also used during the First World War: Methyl chloroformate monochloride, a colourless liquid that is both an irritant and toxic; and Methyl chloroformate trichloride or diphosgene which is found in a liquid state and is more toxic than the former - both theses products were used by the Germans in their "K" and "C" shells and known by the French as Palite and Surpalite. [list]Vesicants or major poisons: naturally highly dangerous as they are colourless and practically odourless. Due to their great volatility they were very persistent. The best known are sulphur ethylene dichloride or Yperite used by the Germans in their yellow cross shells; phosgene, a highly toxic gaseous substance used by the French during the Battle of Verdun; Chloropicrin which is none other than chloroform nitrate, a colourless liquid with a particular odour and highly toxic; Diphenyl loroarsine, a compound of arsenic found in a solid state (blue cross shells), this gas is very persistent. The processes of attack by gas emission This process was first used in 1915, most notably by the Germans. It consisted of creating, using bottles, a toxic cloud which would be blown by the wind towards the enemy trenches. First of all, the Germans used chlorine, indeed it occurred in the form of a gas and so was easy to put in a bottle and more importantly, as its density was 2.5 times heavier than air, it could be easily compressed, making it easier to transport and therefore cheap. In this kind of attack the Germans also used Per-Stoff, Phosgene, Chloropicrin and cyanidric acid. As chlorine did not attack iron, it was stored in cylindrical bottles. For greater safety the Germans had lined the interior of these bottles with lead. At the neck of the bottle was a screw for opening and closing and a valve to allow the evacuation of the gas. A flexible lead pipe was attached to this valve. In order that that the gas could flow out more quickly it was compressed to 120 atmospheres; the bottle could thus be emptied in 2 to 3 minutes. At first the bottles were filled directly in the factory and then the Germans gradually built 40 lorries which would be allocated to the units responsible for the gas attacks. The French and British would use more or less the same materials as the Germans.

The specialised units The Germans set up two regiments specialised in the use of gas, the No. 35 Engineering Regiment (Peterson regiment which would be at Langenmarck on the 22nd April 1915) and the No. 36 Engineering Regiment. Officers, sub-officers and soldiers practically all became specialists. Each regiment comprised two battalions of 3 companies, a company of an ordnance company (equipment) a weather post and a radio post. A battery consisted of 20 bottles. There were 50 batteries per kilometre: 1,000 bottles, or about 20,000 kg of gas. Each team had to dig out the trenches to contain the bottles, camouflaging them so they could not be seen from the air or spotted by patrols. This work was only carried out at night. A regiment could equip a 12 kilometre front (12,000 bottles) in 5 nights. The bottles were transported from the rear either by rail or in carts. To avoid the clanking of metal, the bottles were wrapped in straw. A discharge attack was subject to two important factors: the weather and the layout of the land. In France there were: 3 specialised battalions, the no. 31, 32 and 33 gas battalions, each comprising 3 companies. The importance of the weather conditions Before deciding upon an attack, headquarters had to take into account two very important factors: the direction of the wind and its speed, which must not exceed 3m/sec otherwise the gas would dissipate too quickly; on the other hand, it must not be less than 1.5 m/second or the gas could stagnate and become dangerous for those using it. In addition, they had to wait until the wind blew either directly or sidelong towards the enemy, which was not always the case, because of the fact that the front was positioned facing North West/ South East and the dominant winds were often from the West. The French and British quite often had the advantage. However, in Flanders, especially at the start of the spring, the wind blew towards the North West. They also had to avoid hot weather because of the glare from the ground and heavy rain that quickly diluted the gas. The ideal moment for this type of attack was at daybreak, especially if it was foggy, or conversely at nightfall.

A favourable terrain Most of the German gas attacks took place in Flanders and in Champagne because the terrain there is flat and with little cover: on terrains intersected by valleys or deep hollows, gas carried by the wind might get directed back towards the rear after having ricocheted off a slope; on terrains where there is low vegetation (fields, vines etc.) the toxic cloud may divide in two, the lower part sticking to the vegetation whilst the upper part passed above, losing its power; in wooded terrains the cloud might get stuck in the wood and quickly dissolve, or pass over it to fall several kilometres to the rear. As for water courses, if they were large enough they would retain the toxic cloud and could even absorb it, especially if the gas used was Chlorine. The Gas attack Once the order to attack had been given, the infantry would withdraw, leaving just a few machine gunners in the battery to cover the sappers who would set up the tubes. When the tubes had been buried in the ground, 3m lead tubes were unrolled and laid out along the parapet of the trench. Then the sappers would open the valves and the gas would escape, forming a cloud. With ideal weather conditions and the bottles full of chlorine, the toxic cloud could travel about 30km; it was deadly within a radius of 15 kilometres. A few minutes after it was discharged, foot soldiers in gasmasks would progress through the trenches abandoned by the enemy. This type of tactic was a success for the Germans when they had the element of surprise, but, with the advent of gas masks and better discipline amongst the allied troops on the front line, such attacks gradually became impossible. April 1915 The Germans used gas in combat about fifty times between April 1915 and September 1917. In the spring of 1916 they used up to 500,000 kg of chemical substances and in the spring of 1917 another 300,000. The most spectacular attack, as it was the first ever, took place on the 22nd April 1915 between Bixschoote and Langemarck in Flanders. On the 22nd April 1915, the 35th German Engineering Regiment known as the "Gasregiment Peterson", from the name of its colonel, began to dig trenches along the 7 to 8km front line between Bixschoote and Langemarck, in order to store their bottles of gas filled with Chlorine - the filling station and the equipment depot were at Kortemarck, some ten kilometres to the North on the Dixmude to Tielt road. The order to attack came at 5.24 pm for 6 pm. It lasted 6 to 8 minutes. Each section leader was able to open the required number of batteries. 35 minutes after the end of the discharge of toxic gas, the German infantry had taken 4 kilometres of terrain without firing a single shot - according to an English source, a German deserter had told of this attack a few days previously, but nobody had listened. The companies retreated to escape from the contaminated atmosphere that enveloped them. The Germans, protected by their masks, advanced in compact lines, firing on those men who had not been totally overcome by the poison. The battalion was to suffer 410 dead, including 9 officers and 164 evacuated, including 1 officer. On that day, out of the 15,000 men who were gassed, there were 5,000 dead, 5,000 taken prisoner and 60 canons were recovered.

The widespread use of chemical warfare On the French side, it was not until February 1916 that the first gas attack took place and in total there would be about twenty. They would take place along a 5 kilometre front using 5,000 bottles filled with "Bertolite" (Chlorine) whose impact range was between 10 and 15 kilometres. The advent of protective equipment and the training and discipline of troops were the best means of counter-attack and contributed to limiting the recourse to this method of warfare.