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Bacteria and Bayonets: How Disease Has Impacted American Warfare

From early settlers to 20th-century biological warfare.

bacteria and bayonets header david petriello

Whether inflicted intentionally or otherwise, disease has had a dynamic impact on the outcome of warfare in North America. Columbus and other early arrivals to the continent brought contagions that, while innocuous to swathes of populations in Europe, were highly destructive to Native American communities. European colonists brought diseases like smallpox and measles, which proved to be as deadly as their traditional means of warfare. Every conflict waged on the continent over the coming centuries would be affected in some part by these illnesses.

The American Civil War saw approximately 750,000 deaths, with almost 500,000 of those attributed to illness. Dysentery, pneumonia, typhoid, and malaria were among the infectious diseases that raged rampant on and off the battlefield, regardless of which side of the conflict a soldier fell on. Similar to the racial disparity seen in both the Spanish flu pandemic and the COVID-19 pandemic, a disproportionate number of Black soldiers serving in the Civil War were struck by illness. They died at nearly double the rate of their white counterparts, lacking the nutrition and proper medical care needed to ward off, fight, or treat the diseases that ravaged camps and battlefields. 

Related: Explore History's Deadliest Diseases

Disease would go on to follow the American soldier through such conflicts as the so-called Indian Wars, the Spanish-American War, and the First World War. By the 1910s, pathogens were an accepted factor of warfare. However, while the technological advancements during World War I saw the advent of several new weapons and inventions, such as tanks, stainless steel, and aircraft carriers, it also gave rise to a new perspective on illness’s place in the midst of global conflict. 

In his book Bacteria and Bayonets: The Impact of Disease in American Military History, historian David Petriello traces the impact of illness throughout the centuries. Read an excerpt below, then download the book today.




Bacteria and Bayonets

By David Petriello

The outbreak of World War I would bring many of [author Jack London]’s thoughts to fruition. Chemical agents such as chlorine, phosgene, and mustard gas led to the deaths of an estimated 90,000 on the Western Front, with over a million others affected. Yet attempts to use disease have been shrouded in secret and rumor. From a variety of governmental reports, scientific studies, and the often dubious journalistic work of Wickham Steed, we can begin to piece together a history of the biological program of Germany during the war. The Central Powers seem to have had the most active of the biological programs, or at least the most documented and revealed to the public. 

The main German biological focus appears to have been a campaign to employ anthrax and Burkholderia mallei, or glanders, to infect the horse population of various Allied and neutral nations. The role of the horse both on the battlefield and in industrial life was still prominent enough to make it of strategic concern to both sides. In fact, at the start of the war in 1914 cavalry still accounted for almost one third of most European armies. Undoubtedly, German military planners appreciated the impact that glanders had produced in the Army of Northern Virginia in 1864, and in numerous other wars of the late 19th century.

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As a potential future belligerent and a current supplier of vital supplies to the Allies, the United States became a prime target for just such German sabotage efforts. Numerous physical attacks took place on American soil from 1914–17, most notably against Black Tom Island in New Jersey and the US Navy Yard in California. Biological attacks began just as early, with the Germans attempting to ship horses and sheep already infected with anthrax and glanders to America and other nations in order to start an epidemic. 

Unfortunately this proved to be more difficult, more liable to be noticed, and less effective than beginning an outbreak directly within the enemy nation. For this to happen, German agents would need to bring the bacteria to America, culture it in secret, and then spread it to its intended targets.  Thus the German government began the process of infiltration into the country of German scientists and terrorists.

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One of the first confirmed attempts occurred early in the war and involved a naval officer named Erich von Steinmetz. After sneaking into America, allegedly disguised as a woman and possessing vials of glanders and other bacterial weapons, Steinmetz was tasked with infecting local livestock. Unfortunately for the Germans, by the time the vials were brought to a lab to test the samples, the organisms inside were already dead. 

Undeterred, Berlin simply redoubled its efforts. George W. Merck, president of Merck & Co. and one of the heads of the American biological weapons program in World War II, wrote in 1946 that there was, “incontrovertible evidence … that in 1915 German agents inoculated horses and cattle leaving United States ports for shipment to the Allies with disease producing bacteria.

In order to aid their strategy, the Germans went so far as to set up a biological weapons laboratory in Chevy Chase, Maryland, around 1915. Their agent in this attempt was Dr. Anton Casimir Dilger, a natural born American and son of a Medal of Honor winner. Dilger had been educated in medicine in Germany and was in that nation at the start of the war. Using his American passport, he was able to freely travel between the countries, returning to the United States in 1915 with vials of anthrax and glanders. Along with his brother Carl, Anton Dilger set up a laboratory in Chevy Chase just outside of Washington DC. From here bacterial samples were sent to Baltimore and as far away as St. Louis, in which city Dilger attempted to establish a second production facility.

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Anthrax was sent to fellow German agent Capt. Frederick Hinsch, who lived in a house in Baltimore. Hinsch would go on to disseminate some of his weapons to German agents in New York City. Some of these saboteurs even infiltrated the horse stables in Van Cortland Park in order to infect the animals there. One of the agents was eventually captured, reporting that 

“The germs were given to me by Captain Hinsch in glass bottles about an inch and a half or two inches long, and three-quarters of an inch in diameter, with a cork stopper. The bottles were usually contained in a round wooden box with a lid that screwed on the top. There was cotton in the top and bottom to protect the bottles from breaking. A piece of steel in the form of a needle with a sharp point was stuck in the underside of the cork, and the steel needle extended down in the liquid where the germs were. We used rubber gloves and would put the germs in the horses by pulling out the stopper and jabbing the horses with the sharp point of the needle that had been down among the germs. We did a good bit of work by walking along the fences that enclosed the horses and jabbing them when they would come up along the fence or lean where we could get at them. We also spread the germs sometimes on their food and in the water that they were drinking…. Captain Hinsch spoke often when I met him of different fires that had occurred and of outbreaks of disease among horses and would make remarks about how well things were going.” 

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Yet this promising campaign begun by the Germans would amount to little. While it was reported that additional numbers of livestock were also infected in Norfolk, Newport News, Baltimore, St. Louis, and Covington, it is difficult to trace all of these to German action. Regardless, with the onset of winter most of Dilger’s bacterial samples died off. By 1916 he himself traveled to Germany, perhaps to obtain more bacterial and viral agents. Upon his return to America he became aware that the FBI was quickly closing in on him, forcing him to flee to Mexico, and from there to Spain. 

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Later Dilger became one of the prime participants in the German scheme to bring Mexico into the war against the United States that resulted in the infamous Zimmerman Telegram. Though no massive bacterial or viral outbreak was to erupt in America or cripple its role as a military supplier to the Allies, the fears and lessons of German actions would prove invaluable during World War II and the Cold War.

In addition, the actions of Dilger and others led to fear of domestic terrorism. Various unproven or unfounded stories began to circulate of terrorist actions by various foreign or domestic actors against America. One of the most infamous tales involved infected plasters in 1917. In July of that year, a story began to circulate in local newspapers that a German immigrant was distributing poisoned bandages in both Kansas and Illinois. 

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Various reports claimed tetanus, pneumonia, typhoid, or spinal meningitis to be the infections that would potentially devastate the region. Bauer & Black Company in Chicago quickly denied the story, causing the possibility “ridiculous.” The Department of Justice issued warnings to the public against using the product, which simply fueled the fears and rumor mills then circulating across the nation.

The German Empire soon expanded its biological efforts to the rest of the world as well. On the Eastern Front, attempts were made to infect sheep in Romania bound for export to Russia, hoping to cripple the food supply. Germany was accused of dropping chocolates and toys infected with disease for children in Bucharest. Rumors even began to circulate that Berlin had attempted to unleash the plague in St. Petersburg in 1915. 

Agents were in fact arrested attempting to sneak into both Russia and Romania in 1916. Most notable among these was Baron Otto Karl von Rosen, a Norwegian aristocrat who was captured while attempting to infect horses in his home country with anthrax. In addition, the conquest of Serbia was quickened by a massive outbreak of typhus which decimated the nation’s fighting age population.

On the Western Front, Germany reportedly poisoned French wells in 1917 using the corpses of deceased soldiers. A year later, during the general German retreat, efforts were made to release cholera and glanders upon the advancing Allied forces. 

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Yet again all of these attempts produced no discernible deaths and many may have been baseless accusations reminiscent of similar assertions made against Jews in the Middle Ages, or claims made regarding the Rape of Belgium. Perhaps the only success of the German biological warfare program was the infection of 4,500 mules in Mesopotamia, dramatically crippling British supply lines in the theater, though not changing the outcome of the campaign. 

American biological efforts focused more on prevention than on offensive capabilities. Surgeon General Rupert Blue headed the nation’s health service from 1912 to 1920 and during his tenure and that of his predecessor the military began to mandate more vaccines for its soldiers. As part of this, from 1904 to 1913, 585,000 soldiers and sailors were vaccinated against tetanus. 

During that same nine-year period the armed forces would report only eight cases of the illness, demonstrating the effectiveness of the program. With the outbreak of war, Blue ordered the mass production and stockpiling of vaccinations for tetanus, smallpox, diphtheria, and typhoid by the Hygienic Laboratory. All of these represented preventable diseases that historically caused the most deaths in war. In an effort to reduce the impact of disease, President Wilson in 1917 ordered the Public Health Service to be placed under the umbrella of the US Army, where it would stay until 1921.

Want to keep reading? Download Bacteria and Bayonets today!

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