The history of nerve agents begins on 23 December 1936, when Dr. Gerhard Schrader of the I. G. Farbenindustrie laboratory in Leverkusen first prepared Tabun (ethyl dimethylphosphoramidocyanidate, GA). Schrader had been in charge of a program to develop new types of insecticides since 1934, working first with fluorine-containing compounds such as acyl fluorides, sulfonyl fluorides, fluoroethanol derivatives, and fluoroacetic acid derivatives. In 1935, he prepared dimethylphosphoramidofluoridic acid as a continuation of the previous line of research. He obtained patents for this compound in Germany, the United Kingdom, Switzerland, and the United States, and he began to investigate systematically the dimethylphosphoramides, eventually leading to the preparation of Tabun. Schrader found that Tabun was extremely potent against insects; 5 ppm of Tabun killed all the leaf lice he used in his initial experiment. In January 1937, Schrader was the first to observe the effects of nerve agents on human beings when he and a laboratory assistant began to experience meiosis (contraction of the pupils of the eyes) and shortness of breath because of their exposure to Tabun vapor in the laboratory. As Harris and Paxman noted, Schrader and his assistant "were luck to escape with their lives." ¹

In 1935, the Nazis had passed a decree which required all inventions of possible military significance to be reported to the Ministry of War. A sample of Tabun was sent to the chemical warfare (CW) section of the Army Weapons Office at Berlin-Spandau in May 1937, and Schrader was summoned to Berlin to give a demonstration. At that time Schrader's patent application was made secret. Colonel R½driger, head of the CW section, ordered the construction of new laboratories for the further investigation of Tabun and other organophosphate compounds. Schrader soon moved to a new laboratory at Wuppertal-Elberfeld in the Ruhr valley.

Manufacture of Tabun by Nazi Germany

In 1939, a pilot plant for Tabun production was set up at Munster-Lager, on Luneberg heath near the German Army proving grounds at Raubkammer. In January 1940, the Germans began construction of the full scale plant, code named Hochwerk, at Dyernfurth-am-Oder (now Brzeg Dolny in Poland), on the Oder River 40 km from Breslau (now Wroclaw) in Silesia. The plant covered an area 1.5 by 0.5 miles and was completely self-contained, synthesizing all intermediates as well as the final product, Tabun. The facility had an underground plant for filling munitions, which were then stored at Krappitz (now Krapowice) in Upper Silesia. An IG Farbenindustrie subsidiary, Anorgana GmbH, operated the Tabun plant, as well as all other CW agent production plants in Germany.

The plant took an extraordinarily long period, from January 1940 until June 1942, to become operational. This was due primarily to the difficult nature of the production process. Certain intermediates were so corrosive that the Germans were forced to run all reactions in quartz- or silver-lined vessels. The extreme toxicity of Tabun required that the final production units be enclosed in double glass-lined walls, with a stream of pressurized air circulating between the walls. All units were periodically decontaminated with steam and ammonia.

The Dyernfurth workforce numbered 3,000, all German nationals. Workers were equipped with respirators and clothing made from a rubber/cloth/rubber sandwich; the clothing was discarded after the tenth wearing. Despite these precautions, over 300 accidents occurred before production began, and at least 10 workers were killed during the 2.5 years of operation. Harris and Paxman give some examples of incidents in reference 1:

• Four pipe fitters had liquid Tabun drain onto them and die before their rubber suits could be removed.
• A worker had 2 liters of Tabun pour down the neck of his rubber suit and died within 2 minutes.
• Seven workers were hit in the face with a stream of Tabun of such force that the liquid was forced behind their respirators; only two survived despite heroic resuscitation measures.

Sarin: the Second Nerve Agent

In 1938, a second potent organophosphate nerve agent was discovered. This agent, Sarin (1-methylethyl methylphosphonofluoridate, GB) was named for its four discoverers: Schrader, Ambros, R½driger, and van der L inde. In June 1939, the formula for Sarin was passed to the to CW section of the Army Weapons Office at Berlin-Spandau along with a sample of the compound.

All the synthetic routes for Sarin investigated at that time required the use of hydrogen fluoride, which caused severe corrosion problems. This necessitated the use of quartz- and silver-lined components. Pilot plants were constructed at Spandau, M½nster Lager, on Luneberg heath, and pilot production of Sarin was conducted in Building 144 in Dyernfurth. The Dyernfurth Sarin plant is variously listed as having a capacity of 40 or 100 tons per month A 500-ton per month production plant was under construction at Falkenhagen, southeast of Berlin, at the end of World War II. Estimates vary for the total Sarin production from 500 kg to 10 tons.

The United States began producing Sarin in the early 1950s and ended regular production in 1956.

The Secret of Tabun Gets Out

On 11 May 1943, the British captured a German chemist who had worked at the main Army CW research laboratory in Spandau. The prisoner told the British the code name for Tabun (Trilon 83), the chemical reactions by which it was produced, its effects, and methods of use of and defense against Tabun. This was compiled into an MI9 intelligence report of 3 July 1943. Following the war, the Allies contended that they first became aware of Tabun in April 1945, when a German ammunition dump was captured and a shell containing Tabun was shipped to the United Kingdom for analysis. However, the record appears to show that the responsible officials ignored the 1943 report.

The End of the War

At the end of 1944, Germany had produced 12,000 tons of Tabun: 2,000 tons loaded into projectiles and 10,000 tons loaded into aircraft bombs. These munitions were stored at Krappitz (Krapowice) in Upper Silesia as well as in abandoned mine shafts in Lausitz and Saxony. Some stocks were also transported to Baveria in anticipation of a last ditch defensive stand by the Nazis.

In August 1944, as the Red Army approached Silesia and the Western Allies began the race for the German border, the Nazis began systematically destroying documentation of the research on and the manufacture of Tabun and Sarin. In early 1945, Dyernfurth was to be abandoned and tons of liquid nerve agents were simply poured into the Oder. The plant was rigged for demolition, but the Russians surrounded the plant before it could be destroyed. The Luftwaffe was then ordered to bomb the plant, but they also failed to destroy it. It is believed that the Soviets captured both the full-scale Tabun plant and the pilot Sarin plant intact. The Soviets later captured the near complete full-scale Sarin plant at Falkenhagen. It has been reported that production at Dyernfurth resumed in 1946 under Russian auspices.

Soman

Richard Kuhn discovered Soman (1,2,2-trimethylpropyl methylphosphonofluoridate, GD) in the spring of 1944, while working for the German Army on the pharmacology of Tabun and Sarin. The documents detailing the discovery were buried in a mineshaft 10 miles east of Berlin, where they were discovered by the Soviets and removed. The Soviets produced and stockpiled Soman during the Cold War.

VX

Several chemical companies and other scientists working independently discovered the potency of a class of organophosphate esters of substituted 2-aminoethanethiols in 1952 and 1953. Almost simultaneously in 1954:

• ICI brought Amiton ( O,O-diethyl- S-[2-(diethylamino)ethyl] phosphorothiolate) to market;
• R. Ghosh and J. F. Newman of ICI submitted a manuscript containing the details of this class of compounds ( A New Group of Organophosphate Pesticides, Chemistry and Industry, 1955, 118);
• Schrader, now at Farbenfabriken Bayer AG, prepared S-[2-(diethylamino)ethyl]- O-isopropyl methylphosphonothioate;
• Tammelin at the Swedish government's chemical warfare defense laboratory prepared S-[2-(diethylamino)ethyl]- O-ethyl methylphosphonothiolate and S-[2-(dimethylamino)ethyl]- O-isopropyl methylphosphonothiolate; and
• Ghosh at ICI prepared S-[2-(diethylamino)ethyl]- O-ethyl ethylphosphonothiolate.

A Soviet team form the I. M. Sechenov Institute in Leningrad had already predicted the anticholinesterase activity of S-2-dialkylaminoethyl phosphono- and phosphorothiolates. The British CW laboratory at Porton began investigating this class of compounds, and notified the US CW laboratory at Edgewood, which began a systematic investigation of the entire class. In 1958, the US selected VX ( S-[2-[bis(1-methylethyl)amino]ethyl]- O-ethyl methylphosphonothiolate) for manufacture. Construction of the production plant began in 1959; production ran from 1961 through 1968.

An interesting (and perhaps apocryphal) footnote concerns the chemical structure of VX, which the US government classified as secret until the early 1970s. The Soviets had learned of the toxicity of the class of compounds. They had either learned the molecular formula (C ₁₁H ₂₆NO ₂PS) or they had obtained a garbled version of the structure; as a result, the Soviet V-gas has the structure S-[2-(diethylamino)ethyl]- O-ethyl isobutylphosphonothiolate, a slightly different compound from VX with the same formula. It is also interesting to note that the SIPRI report, published in 1971, (reference 2) states that the formula for VX is secret, but a table in the report with a speculative structure correctly identifies VX.

Locations

References

The historical information on this page comes almost entirely from the two references listed below.

1. Paxman, J.; Harris, R., A Higher Form of Killing : The Secret Story of Chemical and Biological Warfare, Hill and Wang, New York:1982, pp. 53-67, 138-139.

2. Stockholm International Peace Research Institute, The Problem of Chemical and Biological Warfare. A Study of the Historical Technical, Military, Legal, and Political Aspects of CBW and Possible Disarmament Measures. Vol. 1. The Rise of CB Weapons, Humanities Press: New York, 1971, pp. 70-75, 280-282.

These two references both use a series of reports prepared by the British Intelligence Objectives Subcommittee, which debriefed Schrader and his colleagues following the war, as the source for the information concerning Germany's nerve agent program. A partial list of these references (thus far unavailable to the author) includes:

• British Intelligence Objectives Subcommittee, Interrogation of German CW Personnel at Heidelburg and Frankfurt, Report No. 41.
• British Intelligence Objectives Subcommittee, Interrogation of Certain German Personalities Connected With Chemical Warfare, Report No. 542.
• British Intelligence Objectives Subcommittee, The Development of New Insecticides and Chemical Warfare Agents, Report No. 714 (authored by Gerhard Schrader).
• British Intelligence Objectives Subcommittee, Interrogation of Prof. Ferdinand Flury and Dr. Wolfgang Wirth on the Toxicology of Chemical Warfare Agents, Report No. 782.
• Combined Intelligence Objectives Subcommittee, Chemical Warfare, IG Farbenindustrie AG Frankfurt/Main, Report No. 30.
• Combined Intelligence Objectives Subcommittee, Chemical Warfare Installations in the Munster Lager Area, Report No. 31.