German counterintelligence officials also developed elaborate methods to conceal the nerve agent program from foreign intelligence services. Tabun was given a variety of cover names, including “Gelan I” and “Substance 83,” although the preferred designation was “Trilon 83.” The ethyl analogue of Tabun was called “Gelan II” or “Trilon 32,” while Sarin was referred to as “Gelan III” or “Trilon 46.” Chemical ingredients used in the manufacture of Tabun were also designated with code names to make it harder for enemy spies to track shipments. These codes were kept in a secret “black book” and deciphered with the aid of an index. For example, raw materials were coded as follows: ethanol (A4), chlorine (A5), phosphorus (A6), sodium hydroxide (A9), and sodium (A17). Whenever an ingredient for Tabun arrived at Dyhernfurth, it was assigned another local code name, making correct identification nearly impossible if the plant and its records were to fall into enemy hands. The code-name system also had the effect of keeping most of the technical staff in the dark about the precise chemical reactions involved in the manufacture of Tabun.
Because of the elaborate counterintelligence measures designed to protect the secrecy of Tabun and Sarin, the Allies remained unaware of these dramatic developments. A U.S. intelligence report in July 1942 titled “New German Poison Gas” read as follows: “Disclosures relative to so-called ‘Blau Gas’ have occurred numerous times in the past and . . . are no longer seriously regarded. Intelligence reports lend considerable weight that new German agents are not of the nature of so-called nerve gases.” In hindsight, this assessment could not have been more wrong.
DYHERNFURTH HAD its own munition-loading facility, which was built underground and equipped with ventilation shafts. Steel artillery shells and bomb casings were manufactured in a separate building and placed on conveyor belts that transported them to the filling plant. Liquid Tabun pumped from underground storage tanks was loaded into empty 105 mm and 150 mm artillery shells, 250-kilogram aerial bombs, and artillery rockets. Whereas a 105 mm shell contained about a kilogram of liquid agent, a 250-kilogram bomb contained 80 to 85 kilograms. To compensate for Tabun’s lack of volatility, the bombs contained a central “burster” tube filled with a high explosive that, detonated on impact with the ground, would shatter the liquid agent into a mist of tiny droplets, poisoning enemy soldiers through inhalation and skin contact.
Once an aerial bomb had been loaded with Tabun, the filling port was closed with a plug that incorporated a tightening pin. Using a wrench, a technician applied seating pressure to the pin, causing it to shear off and leave the plug in a sealed position, flush with the surface of the weapon. The sealing plug and adjacent surface were then coated with a slow-drying pink lacquer that would turn a deep carmine if Tabun leaked through the plug. Near the base of the bomb or shell, workers painted three green rings around the munition to indicate its contents, along with stenciled numbers providing the date of manufacture and a code letter indicating the ratio of Tabun to chlorobenzene. In September 1942, the first 138 metric tons of Tabun-filled shells and bombs produced at Dyhernfurth were delivered to the Wehrmacht. Packed into crates, the munitions, fuses, and other components were loaded onto trucks and railway freight cars for transport to storage depots controlled by the Luftwaffe and the Army.
When serious shortages of raw materials prevented Anorgana from meeting its manufacturing targets for mustard agent at Gendorf, the Speer ministry decided to give priority to the production of Tabun, ensuring qualitative if not quantitative superiority over the Allies. To increase output at Dyhernfurth, the Nazi regime decided to employ forced prison labor and built a satellite of the nearby Gross-Rosen concentration camp there in early 1943. Known as Dyhernfurth I, the labor camp (Arbeitslager) initially housed some two hundred prisoners, mostly Poles, Russians, Germans, and Czechs.
The forced laborers were assigned the most menial, backbreaking, and dangerous tasks at the Tabun plant, including construction, maintenance, and loading munitions with the liquid agent. On the filling line, they wore protective clothing similar to a deep-sea diving suit, with a helmetlike mask covering the entire head and a hose providing a supply of fresh air. Because of the short length of the hose, the suit permitted only limited movement. Whenever a worker needed to drink or go to the bathroom, he had to remove the mask, exposing himself to toxic fumes. As a result, the forced laborers suffered continually from the symptoms of low-level Tabun poisoning. Those exposed accidentally to a lethal dose were denied medical treatment and left to die.
Prisoners at Dyhernfurth were also exploited for medical experiments involving deliberate exposure to nerve agents. Early in the war, guinea pigs and white rats were found to be inadequate for testing Tabun and Sarin, and apes were used instead because their physiological reactions were closer to those of humans. The Speer ministry purchased a colony of apes from Spain at a cost of 200,000 Swiss francs and transported them to Germany by train, but many of the animals died in transit. Given the difficulty and high cost of procuring nonhuman primates, it was decided to experiment on concentration camp inmates. At Dyhernfurth, about twenty prisoners were exposed to nerve agents for varying lengths of time in a sealed glass chamber and then examined; about a quarter suffered painful deaths during the trials. Prisoners were also misused as human “canaries” by being locked up for long periods without a gas mask in train cars or munitions depots loaded with Tabun-filled bombs or shells.
MEANWHILE, German military scientists continued to search for more lethal and effective nerve agents. Because the mechanism of action of Tabun and Sarin was poorly understood, the research-and-development process was based largely on trial and error. In early 1943, Colonel Schmidt of the Army Ordnance Office asked Professor Richard Kuhn, the director of the Institute of Chemistry at the Kaiser Wilhelm Institute for Medical Research in Heidelberg, to analyze the effects of nerve agents on the central and peripheral nervous systems. As this task had been assigned a high priority, the members of Kuhn’s research team were exempted from military service.
Kuhn, forty-two, was one of Germany’s most eminent organic chemists, having been awarded the Nobel Prize in Chemistry in 1938 for his work on the synthesis of carotenoids and B vitamins (although he had been prevented from accepting the prize). Before the war he had taught for a year at the University of Pennsylvania and had been a prominent member of the international scientific community. After Hitler’s rise to power, however, Kuhn had remained president of the German Chemical Society and served as a consultant to other Nazi Party organizations. He seemed to be an enthusiastic supporter of the regime, giving the Hitler salute at the beginning of his classes and shouting “Sieg heil!” with apparent gusto. Kuhn’s close friends later claimed that he had only feigned support for Hitler to shield academic science from political interference, and that he had retained the presidency of the German Chemical Society to prevent it from being taken over by a Nazi hack. In any event, Kuhn willingly accepted the Army assignment to study the physiological action of the nerve agents.
In conducting this investigation, Kuhn drew on some recent discoveries about the role in the nervous system of a natural chemical substance called acetylcholine. In 1914, Henry Dale, a physiologist at the National Institute for Medical Research in London, had described the physiological effects of acetylcholine on various organs. Then, in 1921, Otto Loewi, a German-born professor of pharmacology living in Graz, Austria, had provided the first proof that chemical messenger substances are involved in the transmission of nerve impulses from one nerve cell to another and from a nerve cell to a responsive organ. Loewi focused on the function of the autonomic nervous system, which governs the activity of involuntary smooth muscles (such as those of the pupil, the heart, and the gastrointestinal tract) and secretory organs (such as the salivary, sweat, and adrenal glands). The autonomic nervous system is in turn divided into two parts, “sympathetic” and “parasympathetic,” with opposing physiological effects. For example, the sympathetic system increases the heart rate, whereas the para
sympathetic system slows it.
In a landmark experiment, Loewi and his colleagues found that by electrically stimulating the vagus nerve (part of the parasympathetic nervous system) enervating the isolated heart of a frog, they could slow the heart’s rate of beating. The investigators then took the saline solution perfusing the frog heart and used it to perfuse a second isolated frog heart in which the vagus nerve had not been stimulated. Surprisingly, the rate of the second heart also slowed, indicating that the nerve ending had released a chemical substance that mediated its physiological effect on the heart muscle. This substance, which Loewi termed Vagussto f, was later shown to be acetylcholine. In 1926, Loewi and his colleague Ernst Navratil demonstrated that acetylcholine is broken down in the body by a specific enzyme, which they named cholinesterase; and in 1929, Henry Dale and Harold Dudley isolated acetylcholine from animal tissue. For their important discoveries, Loewi and Dale shared the Nobel Prize for Physiology or Medicine in 1936.
When Kuhn and his colleagues began their research in 1943 on the mechanism of action of nerve agents, they knew from the work of Loewi and Dale that acetylcholine plays a key role in the parasympathetic part of the autonomic nervous system and in the peripheral nervous system, which provides voluntary control over the skeletal muscles. The arrival of a nerve impulse at the junction between a nerve and a muscle cell induces the release from the nerve ending of molecules of acetylcholine, which diffuse across a narrow gap called the synapse and stimulate receptors on the surface of the muscle cell, triggering a series of biochemical events that cause the muscle fibers to contract. Under normal conditions, cholinesterase enzymes in the synapse immediately break down the acetylcholine and halt the stimulation of the receptors, allowing the muscle fibers to relax. In this way, acetylcholine and cholinesterase operate as a biochemical on-off switch: the messenger substance activates the circuit, and the enzyme breaks it.
Kuhn found that exposing laboratory animals to Tabun strongly inhibited the action of cholinesterase, an effect that he hypothesized was key to the toxic effects of nerve agents. By preventing cholinesterase from destroying acetylcholine, nerve agents freeze the biochemical on-off circuit in the “open” position, allowing the messenger substance to build up to toxic levels. Because acetylcholine plays multiple roles in the peripheral, autonomic, and central nervous systems, excessive amounts give rise to diverse physiological effects. In the peripheral nervous system, a surfeit of acetylcholine causes the skeletal muscles to go into violent, uncontrolled spasm, followed by a state of vibration and then paralysis. In the autonomic nervous system, too much acetylcholine affects the smooth muscles and glands involved in digestion, excretion, and respiration, resulting in pinpoint pupils, excessive salivation, intestinal cramps, vomiting, and constriction of the bronchial tubes. In the central nervous system, acetylcholine overstimulates groups of nerve cells in the brain, causing seizures. Nerve agents can induce death by asphyxiation through three different mechanisms: constriction of the bronchial tubes, suppression of the respiratory center of the brain, and paralysis of the breathing muscles. These diverse effects of excess acetylcholine are collectively known as a “cholinergic crisis.”
Based on these insights, Kuhn’s research team developed a standardized assay that measured the ability of nerve agents to inhibit purified cholinesterase enzymes in the test tube. Over the next two years, they used this assay to screen a variety of candidate nerve agents, some of their own invention and others synthesized by the German Army chemists at Spandau Citadel.
DESPITE GERMANY’S invention of the nerve agents, Hitler held back from unleashing this secret weapon. At the same time, he encouraged the German Army to proceed with production and testing so as to ensure a position of military superiority should the Allies decide to initiate chemical warfare. By the end of 1944, the production of Tabun was slated to rise from 1,000 to 2,000 tons per month.
Meanwhile, the Anorgana company headed by Ambros moved forward with plans for the industrial production of Sarin, which was militarily more effective than Tabun but more difficult to manufacture. Construction of a Sarin pilot plant at Dyhernfurth had been authorized in late 1942, and full-scale production was scheduled to begin in March 1945. Two competing manufacturing processes for Sarin, one developed by Schrader and the other by an army chemist named Reetz, were tested at pilot plants constructed at Spandau, Raubkammer, and Dyhernfurth. Schrader’s process involved a series of five reactions, two of which were highly corrosive and required the use of reactors lined with silver, glass, or fused quartz.
The German Army proposed building a full-scale Sarin production plant with a capacity of 500 tons per month alongside the Tabun factory at Dyhernfurth, taking advantage of common elements in the manufacturing processes of the two agents. But the Luftwaffe objected strongly to this plan on security grounds: if the enemy ever discovered the location of Dyhernfurth, a single air raid could deprive the Reich of its two most effective war gases. Given the desirability of dispersing military production, the Luftwaffe insisted that the full-scale Sarin plant be built at a separate location and operated independently.
Anorgana eventually identified a suitable site in the forest of Falkenhagen near the town of Frankfurt-on-the-Oder, about a hundred kilometers east of Berlin. Before the war, this area had been developed as a proving ground and had a vacuum tunnel for testing ballistic missiles. Falkenhagen offered several logistical advantages: it was connected by road and rail to the nearby town of Brisen, fifteen kilometers away, and had worker housing, a high-capacity waterworks, and a power plant with transformer stations and cables that provided ample electricity. In May 1943, Otto Ambros visited Falkenhagen and approved it as the site of the Sarin facility. Given the code name “Seewerk,” it would be built largely underground and equipped with the most modern production equipment. Whereas the Sarin plant at Dyhernfurth would manufacture 100 metric tons of agent per month with Schrader’s process, the full-scale facility at Falkenhagen would produce 500 tons per month with Reetz’s process.
On May 11, 1943, the British captured a German Army officer in Tunisia. Under interrogation, he revealed that he was a chemist who had done chemical weapons research at Spandau Citadel in Berlin. He described the development of a new warfare agent that was colorless, had little odor, and possessed “astounding properties.” Minute doses made the pupils shrink to pinheads and constricted the bronchial tubes, causing an asthmalike shortness of breath, and higher doses were lethal within fifteen minutes. The informant knew the substance only by the code name “Trilon 83.”
The British interrogators judged the prisoner’s information to be reliable and wrote a ten-page secret report that was sent on July 3, 1943, to Military Intelligence in London and the Chemical Warfare Experimental Establishment at Porton Down. (Founded in 1916 on 7,000 acres of rolling English countryside in Wiltshire, Porton Down was the British government’s primary center for chemical weapons research and development.) Because of a lack of corroborating evidence, however, British officials had doubts about the veracity of the intelligence report and decided to take no action.
ON THE EASTERN front, Hitler’s campaign to conquer the Soviet Union was reaching a fateful turning point. In the fall of 1942, the German Sixth Army had attacked Stalingrad, and during the ensuing weeks, street fighting had raged throughout the city. At dawn on November 19, the Soviets launched a major counteroffensive in which armored spearheads drove in a pincer movement from the north and the south, cutting off Stalingrad and forcing the Sixth Army to retreat to the west or be surrounded. After Hitler refused to authorize a retreat, twenty German divisions were encircled by the Soviet forces. On January 8, 1943, the Soviet commander gave the doomed Sixth Army a final chance to surrender. When Hitler again refused, the Soviets began a massive artillery bombardment with 5,000 guns. Over six days of bitter fighting, the German pocket was reduced by half, and on February 2, 1943, the battered remnant finally surrendered. Of the more than 250,000 German soldiers who fought at Stalingrad, 7
0,000 were killed and 91,000 captured, including 24 generals. Half starved and frostbitten, the POWs were sent to camps in Siberia, and only about 5,000 survived the war. This terrible defeat halted the German advance into southern Russia and provoked much soul-searching in Berlin.
After the debacle at Stalingrad, the proponents of gas warfare in the Nazi inner circle believed that their time had come. Martin Bormann, the head of the Party Chancellery and private secretary to the Führer; Joseph Goebbels, the Reich Minister for Popular Education and Propaganda; and Robert Ley, the leader of the German Workers’ Front, all argued for unleashing Tabun against the Red Army. Hitler was prepared to consider the use of chemical weapons against the Russians, whom he despised and considered subhuman. In February 1943, he ordered preparations for a chemical attack on the eastern front, setting a deadline of April 20. But when that day arrived, he continued to equivocate.
On May 15, 1943, the Führer called a war conference of his closest advisers at his new military headquarters near Rastenburg in East Prussia known as “Wolf’s Lair” (Wolfsschanze). Situated in dense forest, the compound consisted of three concentric circles, each protected by minefields, pillboxes, and an electrified barbed-wire fence that was continually patrolled by SS guards. To enter the innermost zone where Hitler lived and worked, even the most senior officials had to obtain a special onetime pass and be personally inspected by the SS chief of security or one of his deputies.
War of Nerves Page 7
