Napoleon’s Army: The Insects That Defeated It

Napoleon Bonaparte is known to history as one of the greatest military leaders and strategist of all times but insects defeated Napoleon’s army repeatedly despite the fact that he led several successful campaigns during the French Revolutionary Wars, served as Emperor of the French, and dominated Europe for more than a decade fighting against a variety of fluctuating European coalitions. Yet, for all the praise Napoleon received he found that wherever his troops marched or sailed, his biggest opponent was often millions of tiny insects that included the flea, the mosquito, and the louse. 

insects defeated Napoleon's army

Napoleon Bonaparte. Author’s collection.

One of the first insects that Napoleon’s army faced was the flea. This encounter occurred when his 3,000-strong army invaded Syria and stormed several coastal towns. One of the coastal towns was Jaffa, which was secured by high walls and defended by Turks. As Napoleon’s army fought against the Turks, they decapitated and gathered the heads of the French soldiers that they killed and then tauntingly raised them on poles above the walls. On 7 March, Napoleon sent a messenger under a flag of truce to negotiate Jaffa’s surrender. A few minutes later, the messenger’s head was raised on a pole. Thus, when Jaffa fell later that day, Napoleon’s soldiers sought revenge and with unbridled cruelty conducted three days of raping, pillaging, and killing men, women, and children.

Then the flea struck back. During this murderous three-day spree, several of Napoleon’s soldiers suddenly fell ill with fevers, headaches, and delirium. Within a few days, hundreds of French soldiers were sick and suffering with chills, high fever, muscle cramps, seizures, and painful lymph gland swellings called bubos. Headaches and delirium followed, and some stricken victims died with 24 hours. Moreover, it was reported that “during the Syrian campaign, the mortality rate from plague was 92%.”[1]

Napoleon's army facing the flea.

CDC image of a flea. Courtesy of Wikipedia.

It seems that although the plague can be caused by rats, fleas that feed on plague-infested rats can also carry the disease. Furthermore, if humans are near the rats, the fleas can also feed on them. French doctors knew it was the Bubonic plague, but they hoped to prevent panic by declaring it was not. Unfortunately, some soldiers also knew because of the bubos, and some committed suicide rather than let the plague take them.

As more soldiers were stricken, rumors spread that Napoleon had ordered fifty incurable victims of the plague to be poisoned. To stop the rumors Napoleon visited the ill at Jaffa on 11 March 1799 and reportedly “spoke to the sick, encouraged them, and touched their wounds, saying ‘You see, it is nothing.'”[2] Napoleon also decided that the best way to prevent the disease from making further inroads was to distract his soldiers, and so he marched his troops to Acre, where the flea achieved an even great victory at the strategically important walled city of Acre, during the Siege of Acre.

The city had a commanding position on the route between Egypt and Syria, and, furthermore, Napoleon hoped to incite a Syrian rebellion against the Ottomans and threaten British rule in India. The siege began on 20 March, but with the fleas having reduced Napoleon’s army to far less than he planned, he suffered one of his biggest failures. This failure became a major turning point in his invasion of Egypt and Syria. Thus, Napoleon marched his army back to Egypt in May, and, supposedly to quicken his retreat, he ordered plague-stricken soldiers to be poisoned with opium.

Napoleon's army - facing the mosquito

Female mosquito. Courtesy of Wikipedia.

Napoleon’s next tangle was with an even more formidable insect. This time, it was a buzzing mosquito in the Caribbean that carried the disease yellow fever, or as it was called “black vomit.” Napoleon’s army was in Saint-Dominique because a former slave named Toussaint L’Ouverture was causing havoc and inciting revolts. Napoleon wanted him captured, and he had sent his General Charles Leclerc to be in charge of the operation and end the problems with L’Ouverture.

Once Leclerc was there, he found that he had to battle not only L’Ouverture, but also yellow fever. French soldiers bitten by mosquitoes infected with yellow fever quickly discovered they were either lucky or unlucky. The lucky soldiers experienced nothing more than mild symptoms that barely lasted a week. The unlucky soldiers suffered dangerously high fevers, severe muscular pain, excruciating headaches, jaundice, and vomiting (coughing up black material, thereby giving yellow fever the name black vomit). Such symptoms were then often followed by delirium, coma, and death.

General Charles Leclerc. Courtesy of Wikipedia.

Leclerc wrote about the problem on 11 June 1802:

“A man cannot work hard here without risking his life and it is quite impossible for me to remain here for more than six months … my health is so wretched that I would consider myself lucky if I could last for that time! … the mortality continues and makes fearful ravages.”[3]

In the end, Leclerc was one of the unlucky ones as he died from yellow fever on 22 October 1802. One historian wrote, “The West Indies was, quite simply, a deathtrap for whites without immunity to yellow fever.”[4] Ultimately yellow fever killed four-fifths of LeClerc’s soldiers. General Rochambeau (the son of the famous commander-in-chief of the French Expeditionary Forces that helped Americans win their revolution) replaced him, and, just like Leclerc’s soldiers, Rochambeau’s soldiers suffered too. In fact, the effects of yellow fever were staggering. Yellow fever “consumed 20,000 additional reinforcements and Rochambeau capitulated in November 1803. … Only approximately 3,000 men returned to France. Although estimates vary considerably, as many as 50,000 soldiers, officers, doctors, and sailors may have died from yellow fever.”[5]

Napoleon's army facing the louse

Drawing of a louse clinging to a human hair. Robert Hooke, Micrographia, 1667. Courtesy of Wikipedia.

After Napoleon’s army left the mosquitoes and the Caribbean behind, they faced a new deadly threat. This time it was a wingless enemy, an obligate parasite that lived externally on warm-blooded hosts. This deadly enemy was lice, whose main weapon was the typhus they carried.

Lice survive in one of two ways: By feeding on skin and debris or by piercing their host’s skin and feeding on blood and other secretions. Yet, that was not how typhus was spread. Rather the louse fed on fever-ridden humans, and once having ingested the pathogen for typhus, known as rickettsia, the rickettsia reproduce and cause the insect’s gut to rupture, thereby making the disease present in the louse’s feces. Humans then became infected by scratching or rubbing these infected feces into their skin or mucous membranes.

Napoleon’s soldiers were marching to Russia to fight, and war, with its inadequate housing, overcrowding, and malnutrition, which made Napoleon’s army a fertile host for the typhus-infected lice. Moreover, the soldier’s slept on lice-infected mats, and they wore the same uniform daily because they were unable to change. Once the soldiers became infested with lice, the lice burrowed in everywhere, even into the seams of their clothing, which exacerbated the problem because no matter what the soldier did, they could not get rid of them.

Typhus is a terrible disease that caused nineteenth-century German epidemiologist August Hirsch to once remark, “The history of typhus … is the history of human misery.”[6] Once infected, the soldiers were stricken with high fevers that raged for about two weeks and their fevers were followed by red rashes or red eruptions. These rashes or eruptions were then followed by death, with the lice experiencing 100% mortality, and, humans 60-90% mortality, although during epidemic conditions, human mortality neared 100% too.

When Napoleon’s army found itself surrounded by lice, they had no means of escape. Thus, thousands of typhus-infected soldiers were too ill to travel to Russia and were left behind to battle the disease in makeshift hospitals. Contemporary writer John L. Capinera in the Encyclopedia of Entomology maintains:

“By August 25, Napoleon’s main army had lost 105,000 men out of an original 265,000. By September, typhus, the prominent disease, and dysentery had ravaged Napoleon’s armies and some corps were only half their original size.”[7]

Napleon's amry - the night of bivouac

Napoleon’s Army during their retreat from Russia in 1812 by Vasily Vereshchagin. Courtesy of Wikipedia.

What life remained after the typhus-infected lice completed their ravaging was nearly obliterated by Russia’s snowy winter. When Napoleon entered Moscow in 1812, he thought it would fall but “Napoleon’s armies totaled only 100,000 men, an 80% reduction in strength.”[8] The Moscow governor, Feodor Rostopchin, also had other ideas than capitulating to Napoleon’s army. He ordered the city burned to the ground,

With nothing remaining but ashes in Moscow, Napoleon’s supplies quickly dwindled. Napoleon found he had little choice but to withdraw, and in November, his beleaguered and hungry soldiers, dressed in summer uniforms with no means to protect themselves from the cold, moved out. Soon the soldiers found themselves slogging through knee-deep snow, and nearly 10,000 men froze to death on the night of 8/9 November. Thus, ultimately, hypothermia coupled with starvation led to the loss of thousands of soldiers and added to Napoleon’s woes of mass desertions by soldiers, thereby resulting in the collapse of the French military.  


  • [1] Peterson, Robert K.D., “Section III Plague and the Syrian Campaign” in The Napoleonic Campaigns and Historical Perception, at Montana State University.
  • [2] The Periodical, Volume 5, 1914, p. 57.
  • [3] Skolnik, Richard, 1803; Jefferson’s Decision, 1969, p. 28.
  • [4] Section IV, in The Napoleonic Campaigns, at Montana State University.
  • [5] Ibid.
  • [6] Kiple, Kenneth F., Plague, Pox, & Pestilence, 1997, p. 104.
  • [7] Capinera, John L., Encyclopedia of Entomology, 2008, p. 1816.
  • [8] Ibid.

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