The Army’s clinical research with chemical-warfare agents arose out of a profound military and medical emergency: the birth of modern chemical warfare itself, amid the trench fighting of the First World War. During a warm autumn day in 1914, on the Western front at Ypres, in Belgium, German forces buried more than five thousand pressurized cannisters of liquid chlorine, and, at sundown, after the explosions and artillery fire had subsided, they opened them. Chlorine vapor hissed out across the battle-scarred countryside; the toxic fog climbed to five feet, then to thirty feet, while the Allied forces watched, awestruck, unable to comprehend the menace. As Major Samuel James Manson Auld, a British officer, described the scene in 1918, just after the war, “They saw the vast cloud of greenish-yellow gas spring out of the ground and slowly move down wind toward them, the vapour clinging to the earth, seeking out every hole and hollow and filling the trenches and shell holes as it came. First wonder, then fear; then, as the first fringes of the cloud enveloped them and left them choking and agonized in the fight for breath—panic. Those who could move broke and ran, trying generally in vain, to outstrip the cloud which followed inexorably after them.”

As the war progressed, new weapons were unleashed on the battlefield—among them mustard gas, a vesicant, which causes blistering upon contact with skin. When the Second World War began, there was a new urgency to research poison gases, and the work focussed intensively on mustard gas and similar chemicals. In 1941, President Franklin D. Roosevelt appointed Alfred Richards, a respected pharmacologist, to coördinate the wartime medical research. A year later, Richards wrote to the Secretaries of the Army and the Navy, asking their permission to use soldiers as test subjects. “In the study of vesicant gases, investigators are confronted by one major obstacle, namely, that the skin of man is so different anatomically from that of laboratory animals that the latter are relatively useless as subjects for experimentation,” he explained. He argued that human experiments with poison gas were necessary and could be done safely. “In the hands of competent experimenters much can be learned concerning the prevention and treatment of gas burns in men without subjecting them to more than relatively trivial annoyance or disability,” he promised.

Using a Freedom of Information Act request, The New Yorker was able to obtain his letter (click on the documents to expand):

At Edgewood Arsenal, in Maryland, the Army built a gas chamber to advance its clinical research. The chamber—an upgrade of an earlier model—occupied a corner of Building 326, which also housed the Officers’ Club. The structure’s walls, made of tile and brick, gave it a vaultlike appearance. Its door was airtight and forged out of thick metal; it had been salvaged from a First World War Navy ship, as was a porthole that served as its sole window. The chamber was a perfect cube, nine feet in all dimensions. Inside, the only source of light was a hundred-watt bulb mounted behind an explosion-proof shield. No more than seven men would be in the room at any given time. “It has been one of the guiding principles of gassing chamber design at Edgewood to have the animals or subjects occupy less than five percent of the chamber volume,” a classified report from the time, “Gassing Chamber for Human Tests: Construction and Operation,” notes. Army scientists knew from experience that too many people caused the concentration of gas to shift in unpredictable ways.

The classified report explains that the chamber’s equipment was designed to run “completely automatically,” with an attendant necessary only to manipulate the dials and to observe the glass bubblers and the pressurized containers and the ducts used to control the flow of gas. Here is a picture, taken in July, 1944, and included in the report:

In 1993, the National Academy of Sciences published a lengthy study of the experiments and their long-term health effects. “Men who participated in the chamber tests commonly reported that they had originally volunteered to ‘test summer clothing’ in exchange for extra leave time before being sent overseas,” the N.A.S. study, “Veterans at Risk,” concluded. “It was not until they arrived at the test location that they were told about the gas chamber tests and, even then, many were not told to what agent they would be exposed.”

Before the soldiers entered the gas chamber, they were told to line up—sometimes dressed in protective clothing, but sometimes naked—in single file by the door, each man standing a yard from the next, until, at the appropriate time, they would all run inside. They had to run in to insure that the door would not stay open for longer than five seconds; beyond that, it was calculated, too much gas would dissipate. According to protocol, ten seconds before they were set to leave, the attendant would bang on the door, and the men would run out. The classified report says that the door had a handle on both sides, although it is unclear whether the handle worked from the inside.

To test the effectiveness of protective clothing, Army and Navy scientists designed so-called “man-break” tests. Soldiers were suited up in protective clothing and wore gas masks, and remained in the gas chamber for between one and four hours. During that time, in addition to withstanding the gas, they had to contend with intense heat and humidity, which could also be controlled; the idea was to simulate a jungle environment. After the experiment, the men would remove their gas masks but were ordered to continue wearing the contaminated clothing, sometimes for as long as a day. Then they were examined. If no burns were found, they were ordered to return to the gas chamber—every day, if necessary—until they did get burned. Some of the tissue damage was widespread, and took more than a month to heal.

According to the National Academy of Sciences, “Those who became sick during the ‘man-break’ tests reported being threatened with court martial if they did not continue the test and reenter the gas chambers. Some even reported that they saw other subjects collapse in the chamber and that they never saw these men again after they were removed from the chamber. In all such cases, the men reported that they had assumed the person had died. Other men recalled that the chamber door could not be opened from the inside and that this frightened them by making them feel trapped.”

Although the number of soldiers tested during the Second World War is unknown, by February, 1945, the chief of the Chemical Corps’s Medical Division had sent letters to more than a thousand soldiers, commending them for “subjecting themselves to pain, discomfort, and possible permanent injury for the advancement of research in protection of our armed forces.”

One Navy volunteer, Glenn M. Holocomb, later claimed that he suffered eye problems, dizzy spells, migraines, chronic hoarseness, and nervous disorders, and had scars. Using a Freedom of Information Act request, The New Yorker obtained part of his medical record from 1945, the year after his test:

The Second World War has been called “the unfought chemical war.” After the Nazi regime fell, American intelligence operatives learned that the Reich had been investing in a new class of chemical weapons, called nerve agents—tabun, soman, and sarin—which Hitler had never used. These chemicals are virtually odorless and tasteless, and infinitesimal amounts can kill a human being in a matter of minutes. As news of the new chemicals circulated, an American military officer proclaimed, “The reign of mustard gas, which has been called the King of Battle gases since it was first used in July 1917, will probably come to an end.”