Hektoen International

A Journal of Medical Humanities

Washington’s deadliest enemy

Kathryn Tone
Wiesbaden, Germany


 George Washington, John Trumbull, 1790

As Commander of the Continental Army, General George Washington is famously remembered for the surprise 1776 Christmas attack on the Hessian garrison in Trenton, New Jersey. A bold, relatively spontaneous decision, the attack was a last-ditch effort to salvage some sort of victory after some punishing eight months of humiliating defeats from the British army and their Hessian partners. While the Battle of Trenton may be one of Washington’s most legendary strategic decisions, it was not the most important. Up against an invisible, ubiquitous enemy, which was deadlier than British cannons or Hessian swords, Washington issued an order on February 5, 1777 to inoculate the entire Continental Army against smallpox. It was the first mass inoculation in military history. Washington’s order, replete with risks and in defiance of a Congressional ban against inoculation, not only saved the army from destruction, and hence the Revolution from collapse, but also thousands of civilian deaths. Beyond the tactical value, the vaccination decision was also a powerful affirmation of the Enlightenment ideals upon which the American Revolution was founded.

Smallpox was brought to the colonies by ships from Europe and Africa bearing immigrants and slaves. Like the Native American population, most of the colonists had not been exposed to it and had no immunity. The major port cities of Boston, Philadelphia and Charleston, with their denser populations and visits from foreign ships, experienced epidemics every five to ten years. During these outbreaks, smallpox was responsible for 10–20 percent of annual overall deaths.1 The highly contagious nature of smallpox made it almost impossible to contain. The variola virus can survive for weeks without a human host. Victims can be infected by direct contact with others, or by merely inhaling dried particles clinging to clothing, cloth, or other inanimate objects exposed to a sickroom or previous victim. Colonial precautions against infection were rudimentary and insufficient. Ships were moored mid-harbor until the cargo, crew, and passengers had been inspected, but often passengers disembarked before this process was complete. Once the disease began spreading, victims were quarantined. However, many could travel before realizing they had been infected, thus carrying smallpox back to their isolated farms and villages. Some survived and carried a natural immunity to the disease. George Washington was one of these lucky few. At the age of nineteen he was exposed to the virus during a trip to Barbados in 1751. Washington emerged with light scarring on the side of his nose. Nothing is known about the intensity of his bout as his daily diary entries stopped for twenty-four days, but one can assume he suffered the full course of the illness—intense headache, fever, vomiting, backache, and the eruption of sores, which ended in the telltale pockmarks.

The technique of inoculation against small pox, commonly referred to as “variolation,” in which a small amount of pus from a smallpox sore was inserted into an incision on the subject’s arm, had been documented in Africa and China as early as 1549. Despite its apparent success in other countries, variolation was viewed with intense distrust, both scientific and religious, and was banned throughout the colonies. However, a particularly devastating outbreak in Boston in 1721 led a prominent physician, Zabdiel Boylston, to experiment with variolation first on his son and two servants, then others. The results were impressive—six of Boylston’s 250 vaccinated patients died. In contrast, the rest of the 5,759 smallpox victims in Boston died at a rate of over one in six.2 But the controversy over variolation remained. Ironically, at the same time of the Boston epidemic and based partially on Boylston’s discovery, the British began vaccinating the general population, thus giving the future invaders of the American colonies immunity to the deadly disease.

Immediately upon taking command of the fledgling Continental army in 1775, George Washington was confronted with the dire threat of smallpox. An epidemic was raging in Boston, exacerbated by the scarcity of food brought on by the port closure and British occupation. Washington’s initial, multi-pronged response mirrored that used traditionally in the colonies. Refugees were barred from entering Army camps; infected civilians were sent to a smallpox hospital in nearby Brookline and a separate hospital was established in Cambridge for soldiers who showed symptoms. When the city was evacuated by the British the following spring, only soldiers who bore the pockmarked scars of having survived the disease were initially allowed to enter Boston. Despite these precautions, smallpox infiltrated the troops and continued to be the leading cause of death. Poor hygiene in overcrowded camps contributed to the dire conditions. In contrast to the professionally trained armies they were up against, the newly formed American army lacked experience and camp discipline, particularly in the area of keeping their water supply clean. By the summer of 1776, 25 percent of the troops gathered in New York in response to the June invasion by British and Hessian troops were listed as too ill for duty. In September, the sick list reached 32 percent.3 Letters during this time indicate that Washington was considering the idea of mass inoculation, but the military situation was too unstable. Following the success of expelling the British from Boston, the Continental army had suffered a string of shattering defeats and was being pursued by the enemy across large swaths of territory. Not a man could be spared. The ignominious fall of Fort Lee in November resulted in huge supply losses—ammunition, tents, clothing, supplies—all captured or destroyed as winter approached.

In January of 1777, with the remaining troops settled predominately in Morristown, New Jersey for the winter, Washington had to reevaluate his strategy. By February he was ready to move forward with a complete vaccination plan. The timing of this change in his thinking can be attributed to shifts in both tactics and circumstances. First, after the overwhelming routs of the previous eight months, it became clear to Washington that the preservation of the Continental Army as a whole took precedence over winning battles and controlling territory. Disease continued to be the biggest threat to the army and his earlier attempts at isolation and quarantine had failed. Second, a fear of smallpox was hindering the recruitment of new soldiers. Some soldiers and officers inoculated themselves in secret, despite the Congressional ban against it, but these unquarantined individuals only helped to spread the disease further. Smallpox’s decimation of the American forces sent to invade Canada in late 1775 was partially due to self-inoculations. Third, the winter pause in fighting presented Washington with the best opportunity to conduct an extremely risky operation. The length of the variolation process was a minimum of three weeks, during which the troops would be incapacitated and vulnerable to attack. Although soldiers from the Continental Army and local militia conducted some guerilla warfare that winter, large scale attacks from the British were not anticipated.

The last contributing factor to Washington’s decision was primarily psychological. Recent victories at Trenton and Princeton had infused the American army and supporters of the Revolution with a desperately needed morale boost. As the news spread around the country and the globe that an army of citizen-soldiers had bested troops from the most powerful army in the world, Washington’s stature and clout increased dramatically. He seized the momentum and shifted his tactics on smallpox completely. Rather than continuing to deal with the disease from a defensive position (trying to avoid or contain it), Washington was ready to go on the offensive and eliminate it completely. The results of the vaccination order were tremendous. By the end of 1777 up to 40,000 troops had been inoculated and the smallpox infection rate in the American army fell from 17 percent to 1 percent.4 Congress quickly moved to legalize variolation throughout the colonies, thus saving thousands more from a once unstoppable disease.

Washington’s inoculation order, strategically invaluable in protecting the Army and thus the fight for independence, was also a manifestation of the Enlightenment ideals which spurred the Revolution itself. Enlightenment thinking favored trust in science as a rational means to improve the human condition, as opposed to the predetermined will of God. Like most of the founding fathers, Washington’s belief in the power of science did not conflict with his religious views. Taking on smallpox to protect the army was not interfering with divine providence, rather it emulated the fundamental idea of the American Revolution—men controlling their own destiny. A massive vaccination of troops in the midst of war was a bold, risky experiment, but so was the creation of the world’s first independent, democratic country. The success of both were unquestionably intertwined and possible thanks to the vision and courage of George Washington.



  1. Shachtman, Tom. Gentlemen Scientists and Revolutionaries: The Founding Fathers in the Age of Enlightenment. St. Martin’s Press, 2014.
  2. Thachter, James. The American Medical Biography of 1828. New York, Milford House, 1967.
  3. Hackett Fischer, David. Washington’s Crossing. Oxford University Press, 2004.
  4. Pomeroy, Ross. “How George Washington Used Vaccines to Help Win the Revolutionary War.” Real Clear Science, last modified September 25, 2016, https://www.realclearscience.com/blog/2016/09/how_vaccination_helped_win_the_revolutionary_war.html.



KATHRYN TONE is a former teacher and aspiring historical novelist. An avid Revolutionary War fan, she recently completed her first book, The King’s Broad Arrow.


Highlighted in Frontispiece Volume 10, Issue 3– Summer 2018
Winter 2018  |  Sections  |  Infectious Diseases

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