Although death in battle is the most obvious form of war-related mortality, in many eras, the deadliest killer was not the opposing army, but epidemics. Throughout history, where armies go, disease has followed.

Often, epidemics have turned the course of history. During the fifth century B.C., the Persian Empire tried to invade Greece several times. Although the world remembers the valor and sacrifice of the Spartans before the Gates of Fire at the Battle of Thermopylae, it was not Sparta, but disease that ultimately checked the Persian advance. Xerxes entered Thessalonia with 800,000 soldiers, and plague and dysentery whittled his army down to 500,000, if the numbers recounted by contemporary historians are to be believed.

In his History of the Peloponnesian War, Thucydides noted that a prophecy predicted that “a Dorian war shall come, and with it, death.” Whether fated or not, the plague that struck Athens during that war (431–404 B.C.) had devastating consequences for Greece during the Classical Age.

According to Thucydides, the plague struck Athens during the first days of summer when Attica, the region of Greece where Athens is located, was invaded and laid waste by the Lacedaemonian army. Soon the epidemic, which was likely carried in by the foreign soldiers, struck. People were suddenly afflicted by high fevers, and then by upper-respiratory problems, including a severe cough. Their skin was covered with pustules that spewed forth “discharges of bile of every kind named by physicians.” Yet the body did not waste away, so that when victims died in seven days or so, they still had some strength. Those who survived past the seventh day usually succumbed to severe diarrhea. So virulent was the disease, Thucydides wrote, that even animals that scavenged the dead died.

As bad as the epidemic was for its victims, some think that its worst effects were on the body civic. In a pattern repeated time and again, society faltered under the strain of so many dead in so brief a time. Athenians were faced with a harrowing choice. They could tend to their friends and family as honor dictated and risk death, or abandon the sick to save themselves. As Thucydides wrote, ”Perseverance in what men called honor was popular with none. . . . Fear of gods or law of man there was none to restrain them.”

Athens was not alone in its extremity, and the city-states of Greece, softened by disease and exhausted by the internecine fighting, were easy targets for an aggressive northern neighbor. When Philip of Macedon and his son Alexander sought to expand their kingdom, Greece fell easily, which ended the Golden Age.

Recent medical anthropology has made some provocative suggestions about the nature of the Athenian plague. It is usually assumed that Athens suffered bubonic plague or typhus. Yet Thucydides’ own description suggests another possibility. He wrote that it began in Ethiopia above the Nile headwaters and then moved north into Egypt and the rest of the Mediterranean basin. Given that account and various other historical descriptions, some modern medical historians have suggested that the plague might have been a form of Ebola.

In any event, in 1994–1995, a subway-building project in Athens revealed a hurriedly dug mass grave near an ancient cemetery. The placement of the skeletons showed that the bodies had been thrown in the grave with little care. Normally, the ancient Greeks burned their dead when they could. The plague struck Athens in 427 BC. The mass grave was dated to sometime between 430 and 426 BC.

Epidemics and war
Much of military history is actually the story of how battles and campaigns correlated with diseases occurring in both the military and the civilian populations. Indeed, medieval and early modern history is a continuing chronicle of the cycle of invasions and epidemics.

The Crusades to free the Holy Land from Saracen control introduced Europeans to new diseases, and vice versa. During the siege of Antioch in 1098, in addition to human losses, an epidemic killed most of the Crusaders’ horses. In an age in which an armored man on a horse was the ultimate fighting machine, a knight without a horse was worse than useless. Later, in the Second Crusade, King Louis VII of France led his army through Europe to Byzantium. According to contemporary chroniclers, plague reduced his army of a half-million soldiers to a mere handful.

In 1566, Holy Roman Emperor Maximillian II and his army of 80,000 prepared to invade Hungary, which was then under Turkish domination. The Germans were checked not by the Turks but by a typhus epidemic; similarly, the Swedes lost control of Russia in 1708 because of the bubonic plague.

In the late 18th and early 19th centuries, Napoleon faced his greatest resistance not from the British navy but from microorganisms. French forces were routed in Syria and Egypt by plague. Of Napoleon’s wars, his Russian campaign stands out as a classic example of strategic blundering. Many students of history know that the Russian winter proved to be as implacable an enemy as the czar’s forces, destroying the emperor’s army. Yet fewer know how badly that army had already been whittled down by typhus. Of the 320,000–600,000 soldiers (accounts vary dramatically) who left France, 70% succumbed to typhus before they reached Moscow. Russian delaying tactics allowed typhus to ravage the remainder. Thus, Napoleon was left with only 50,000 soldiers to occupy Russia. After the winter killed still more troops, only 3000 returned to France.

The 19th century saw still more wars whose outcomes were determined as much by disease as weapons. In the Crimean War (1854–1856), for example, 10 times as many British soldiers died from dysentery as from Russian bullets. The French and Russians suffered similarly.

During the American Civil War (1861– 1865), the vast majority of deaths on both sides were due to disease. Prison camps like Andersonville were notorious for the prevalence of disease; incarceration was a virtual death sentence.

During the Boer War (1899–1902), the British lost about 5 times as many soldiers from disease as from Afrikaner weapons. In the Russo-Japanese war (1904), however, the Japanese, by virtue of stringent health police measures and inoculation, reversed the trend. Japan lost 4 times as many soldiers from enemy fire as from disease.

In the modern history of disease and warfare, World War I stands out. For hard on the heels of the “war to end all wars” came a pandemic, a new and terrible variant of the relatively benign influenza. Despite its deadliness and devastation, the influenza pandemic has receded from memory. So serious was its impact in the United States that society came close to dissolution, as towns and cities shut themselves off and people abandoned one another, just as the Athenians had done 2000 years before.

The pandemic started with soldiers in the trenches (although there is evidence that it was originally brought by recruits from the United States to France and then back again). When the war ended and the troops returned home, they brought influenza with them. From military bases it spread outward, killing a half-million people in the United States and tens of millions more worldwide. Influenza usually kills the weak on both ends of the age continuum, but the 1918 strain killed otherwise healthy adults aged 20–40. In the United States, the flu dead reached such hideous proportions that undertakers ran out of coffins and morgues overflowed.

As rapidly as it struck, the flu vanished. The story continues today, however, as molecular biologists examine tissue samples taken in 1918 as well as bodies exhumed in 1997 from the Alaskan permafrost to determine the nature of the mutation.

The end of the cycle
Although George Washington had his men inoculated against smallpox during the American Revolution, the correlation of war and disease came to an end, at least for industrialized countries, only with World War II. As noted, typhus has been the perennial bane of armies throughout history. This disease, which is caused by rickettsia, was found to be transmitted by ectoparasites such as lice and fleas—in humans, it is transmitted by the body louse, Pediculus humanus. When the louse feeds, it bites its host, who, in turn, scratches. This breaks the skin and allows the louse’s rickettsia-infested feces to enter. In other words, humans infect themselves.

With the discovery of the insect vector came the possibility of controlling typhus through pesticides, which was accomplished during World War II. Endless dustings of DDT were used to control lice. Equally profound was the influence of new antibiotics that were developed and mass-produced during the conflict. These compounds helped destroy the link between warfare and mass disease, at least among the technologically more advanced nations.

In the developing world and in the pockets of poverty and destruction in the West, however, where civilian populations are not or cannot be reached by contemporary medicine, the clutching death of the camp-follower, disease, retains its age-old power.

Suggested reading

1. Epidemics and Military Battles. everest.ento.vt.edu/IHS/militaryEpidemics.html (accessed April, 2001).
2. Kolata, G. Flu: The Story of the Great Influenza Epidemic of 1918 and the Search for the Virus that Caused It; Farrar, Strauss, and Giroux: New York, 1999.
3. McNeil, W. H. Plagues and Peoples; Anchor Books: Garden City, NJ, 1976.
4. Patho-Factlets: Examples of How Disease Altered History. www.science-projects.com/Pathlets.htm (accessed April, 2001).