Despite the creation of Chadwick’s prison camp lab, despite the determination of Bohr and Rutherford to maintain the flow of scientific information across national boundaries, the First World War challenged international cooperation and threatened republican scientific loyalties. It did so in part because many scientists in the belligerent nations went to work for their governments and helped develop weapons that destroyed men in the name of national honor, security, or purpose. Probably the most notorious of these, and a sobering harbinger of nuclear arms, were chemical weapons, often (though not always) dispensed in the form of poisonous gas. Near the Belgian town of Ypres, at 5.00 in the afternoon on 22 April 1915, the air was suddenly filled with ‘thick yellow smoke... issuing from the German trenches’. ‘What follows’, reported the British Field Marshall Sir John French, ‘almost defies description. The effect of these poisonous gases was so virulent as to render the whole of the line held by the French... practically incapable of any action at all... Hundreds of men were thrown into a comatose or dying condition, and within an hour the whole position had to be abandoned, together with about fifty guns.’ There were estimates that 5,000 soldiers died in the attack, and twice that number were injured, their throats and eyes and lungs left burning and their memories haunted. ‘It was’, wrote a British clergyman who observed the retreat, ‘the most fiendish, wicked thing I have ever seen.’13
The Germans had been thinking about chemical weapons since at least the previous year. From the first, German military officials had involved academic and industry chemists in the quest for an agent that would disorient and damage enemies dug into trenches on both fronts. They experimented in the fall of 1914 with a compound that caused violent fits of sneezing, pouring it into howitzer shells and launching them at the French at Neuve Chapelle in October. The compound dispersed poorly and had no apparent effect on the battle, and the shortage of shells and launchers made continued experiments unattractive. The eminent chemist Fritz Haber found a solution: disperse chlorine gas from metal cylinders, creating a toxic cloud that would settle over enemy positions. The German command agreed to try this. The generals recruited scientists and soldiers to serve as forward observers—that is, to find the most favorable positions from which to launch the gas cloud. Six thousand cylinders were opened simultaneously that April afternoon. The cloud at first looked white, then intensified to yellow and green as the amount of chlorine in it rose, drifting higher and moving south and west over French and Algerian posts. The affected soldiers broke and ran.14
Among those Germans sent to plan the attack was Otto Hahn, already well known for his work on radiation with Ernest Rutherford in Montreal. Haber pressed Hahn into service in the name of science and loyalty to the German state. By his own account, Hahn was not so sure, objecting that the use of gas would violate the Hague Convention of 1899, which proscribed the use of projectiles to diffuse ‘asphyxiating or deleterious gas’. Haber responded, first, that the French had already started it, having filled rifle cartridges with tear gas (a dubious claim when Haber made it, in January 1915), and, more important, that the use of gas would ultimately save lives on all sides because it would end the war sooner. It was also technically true that the release of a gas cloud did not involve launching projectiles. Hahn evidently accepted this logic. ‘I let myself be converted’, he remembered, ‘and threw myself into the work wholeheartedly.’ He remained involved in chemical warfare, and was called a ‘gas pioneer’, until the armistice—even after Haber had confided to him that he thought the war was lost.15
The Germans continued to develop new chemical compounds and new ways to deliver them. Shells came largely to replace clouds released from cylinders; chlorine was succeeded by phosgene and chloropicrin, harder than chlorine to detect and more destructive. In the summer of 1917 they fired at Ypres shells marked with a yellow cross and filled with mustard gas, which smelled like horseradish and was, according to one commentator, ‘the war gas par excellence for the purpose of causing casualties’. Men were blinded, in some cases permanently, about seven hours after exposure to it. German use of gas increased especially on the Eastern Front, where prevailing winds favored the emissions and where the Russians were slower than the Western Entente combatants to develop effective gas masks. Hahn helped to coordinate a chlorine and phosgene attack against Russians in Galicia in June 1915. The Russians were taken by surprise, and, as Hahn advanced with German troops, he found their enemies in extremis. ‘We tried to use our own respirators to help some of them, to ease their breathing, but they were past saving,’ Hahn wrote. His conscience prickled. But he and Haber were hardly alone in the work: they were joined by several noted chemists and the physicist James Franck, who would later join the Manhattan Project and urge that atomic bombs not be dropped on Japan. Some 2,000 German scientists all told were involved in chemical warfare in 1914-18.16
Neither were the Germans alone in the work. The French, as Haber seems to have anticipated, were at the time of the chlorine cloud attack at Ypres at work on tear-gas bullets and grenades. Prominent Britons condemned the use of gas—Arthur Conan Doyle charged that the Germans had ‘sold their souls as soldiers’, and Lord Kitchener insisted that ‘these methods show to what depths of infamy our enemies will go’—but the British quickly set to the task of manufacturing chemical weapons and masks to protect their solders against their use. The Allied response-in-kind to the German attacks was uncoordinated and fitful. The British worked hard at developing chemicals, but their way to success was slowed by bureaucratic competition, panic-induced haste, and an official willingness to entertain, at least, crackpot suggestions by amateurs that the British set fire to the atmosphere or spray German lines with amyl nitrate, an inflammable liquid. Hand grenades filled with what were described as ‘annoyers’ were rushed to France in May 1915, and the Scottish physiologist J. S. Haldane devised defenses against gas that involved breathing through a bottle loosely filled with dirt or a urine-soaked sock. French military headquarters, as L. F. Haber (Fritz Haber’s son) has described it, ‘was all energy and valorous sentiments’, but was unable to produce much: the French lacked chlorine to make that gas, and plans to retaliate against the Germans with gas-cloud attacks foundered on command’s decisions to build gas squads largely from wounded soldiers. The French did manage to fill some 50,000 shells with a tear gas that dispersed so rapidly that the targeted Germans appeared not to notice they had been gassed. Even the Russians blustered about making gas clouds—threats, as Haber notes, that were never taken seriously by anyone.
The US president Woodrow Wilson entreated the European belligerents not to use chemical weapons in May 1915. But the United States itself had not signed the 1899 Hague Convention; its delegate, Admiral Alfred Thayer Mahan, said then that he could see no distinction between killing unsuspecting men by explosive or gas. The United States did ultimately agree to an international ban on the use of poison (codified in Hague II, 1907, and signed by the United States soon after), but, like the other signatories, the Americans found ways to evade the ban, and, once the United States had entered the war in April 1917, the Wilson administration, as Haber writes, ‘took gas very seriously indeed’. Responsibility for developing chemical weapons and protection against them was at first given to the US Bureau of Mines, though in June 1918 it was taken on by the Chemical Warfare Service, which undertook both research into and the production of chemicals. American University in Washington DC became in mid-1917 the center of chemical investigation, absorbing work done previously at other universities, though retaining branch laboratories at several. In marshland 20 miles east of Baltimore, the Americans built an enormous chemical manufacturing complex called ‘Gunpowder Reservation’, later the Edgewood Arsenal. The plant employed thousands of men and women, and produced chlorine, phosgene, chloropicrin (which caused weeping and vomiting and which defeated then-existing gas masks), mustard, and several others. By the summer of 1918, Edgewood was contributing heavily to gas warfare on the Western Front. As the Armistice neared that fall, an American observer could not conceal his dismay: ‘Here is a mammoth plant’, he wrote of Edgewood, ‘constructed in record time, efficiently manned, capable of an enormous output of toxic material, and just reaching its full possibilities of death-dealing at the moment when news is hourly expected of the signing of the Armistice. What a pity we did not possess this great engine of war from the day American troops first sailed for France.’18
Casualty figures for those gassed during the First World War are elusive. Estimates made during the two decades following the war ranged from 560,000 to nearly 1.3 million dead or injured. L. F. Haber refuses to try to count Russian casualties—the figures are wholly unreliable, he says— and estimates about half a million gas casualties. While many more men were killed or wounded by explosives or bullets, these are nevertheless substantial numbers, and use of gas later caused reflection and remorse among some of the chemists who had participated in its manufacture. Otto Hahn struggled to absorb the sight of Russians killed by his chlorine cloud in Galicia in 1915. One of Hahn’s contemporaries, Hermann Staudinger, argued that scientists ought to renounce the use of chemical weapons and work to educate their fellow citizens about the special horrors of gas. (Staudinger’s suggestion brought a sharp rebuke from Fritz Haber.) Some American scientists expressed disgust with gas; in France, an eminent chemist urged that chemistry not be used for destructive purposes. Two weeks after the Armistice, a group of British medical researchers, in a letter to The Times of London, criticized the use of gas because (they said) it could not be contained to military targets and because it killed in a particularly heinous way. Sir Edward Thorpe decried ‘the degradation of science’ that resulted from the battlefield use of gas. For scientists to contribute to the death of innocents at the behest of the state was wrong. The critics of gas were to some extent vindicated by future decisions: chemical weapons were evidently not used in the Second World War, and only in a few other instances—by the British against Bolsheviks in 1919, by the Italians against Abyssians in 1935, and by the government of Iraq, against Iran and its own citizens, in the 1980s and 1990s—during the twentieth century.