Siege of Fort Pitt
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The siege of Fort Pitt took place during June and July 1763 in what is now the city of
Pittsburgh Pittsburgh ( ) is a city in the Commonwealth (U.S. state), Commonwealth of Pennsylvania, United States, and the county seat of Allegheny County, Pennsylvania, Allegheny County. It is the most populous city in both Allegheny County and Wester ...
,
Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...
,
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
. The
siege A siege is a military blockade of a city, or fortress, with the intent of conquering by attrition warfare, attrition, or a well-prepared assault. This derives from la, sedere, lit=to sit. Siege warfare is a form of constant, low-intensity con ...
was a part of
Pontiac's War Pontiac's War (also known as Pontiac's Conspiracy or Pontiac's Rebellion) was launched in 1763 by a loose confederation of Native Americans dissatisfied with British rule in the Great Lakes region following the French and Indian War (1754–176 ...
, an effort by Native Americans to remove the Anglo-Americans from the Ohio Country and
Allegheny Plateau The Allegheny Plateau , in the United States, is a large dissected plateau area of the Appalachian Mountains in western and central New York, northern and western Pennsylvania, northern and western West Virginia, and eastern Ohio. It is divide ...
after they refused to honor their promises and treaties to leave voluntarily after the defeat of the French. The Native American efforts of diplomacy, and by siege, to remove the Anglo-Americans from Fort Pitt ultimately failed. This event is best known as an early instance of
biological warfare Biological warfare, also known as germ warfare, is the use of biological toxins or infectious agents such as bacteria, viruses, insects, and fungi with the intent to kill, harm or incapacitate humans, animals or plants as an act of war. Bio ...
, in which
William Trent William Trent (February 13, 1715–1787) was an American fur trader and merchant based in colonial Pennsylvania. He was commissioned as a captain of the Virginia Regiment in the early stages of the French and Indian War, when he served on the wes ...
from an American settler family and Simeon Ecuyer, a Swiss mercenary in British service, gave items from a
smallpox Smallpox was an infectious disease caused by variola virus (often called smallpox virus) which belongs to the genus Orthopoxvirus. The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (WHO) c ...
infirmary as gifts to Native American emissaries with the hope of spreading the deadly disease to nearby tribes. The effectiveness is unknown, although it is known that the method used is inefficient compared to respiratory transmission and these attempts to spread the disease are difficult to differentiate from epidemics occurring from previous contacts with colonists.


Background

Fort Pitt was built in 1758 during the
French and Indian War The French and Indian War (1754–1763) was a theater of the Seven Years' War, which pitted the North American colonies of the British Empire against those of the French, each side being supported by various Native American tribes. At the ...
, on the site of what was previously
Fort Duquesne Fort Duquesne (, ; originally called ''Fort Du Quesne'') was a fort established by the French in 1754, at the confluence of the Allegheny and Monongahela rivers. It was later taken over by the British, and later the Americans, and developed a ...
in what is now the city of Pittsburgh, Pennsylvania, United States. The French abandoned and destroyed Fort Duquesne in November 1758 with the approach of
General A general officer is an Officer (armed forces), officer of highest military ranks, high rank in the army, armies, and in some nations' air forces, space forces, and marines or naval infantry. In some usages the term "general officer" refers t ...
John Forbes's expedition. The
Forbes expedition The Forbes Expedition was a British military expedition to capture Fort Duquesne, led by Brigadier-General John Forbes in 1758, during the French and Indian War. While advancing to the fort, the expedition built the now historic trail, the Forbes ...
was successful in part because of the
Treaty of Easton The Treaty of Easton was a colonial agreement in North America signed in October 1758 during the French and Indian War (Seven Years' War) between British colonials and the chiefs of 13 Native American nations, representing tribes of the Iroquois, ...
, in which area American Indians agreed to end their alliance with the French. American Indians—primarily the Six Nations,
Delawares The Lenape (, , or Lenape , del, Lënapeyok) also called the Leni Lenape, Lenni Lenape and Delaware people, are an indigenous peoples of the Northeastern Woodlands, who live in the United States and Canada. Their historical territory includ ...
and
Shawnee The Shawnee are an Algonquian-speaking indigenous people of the Northeastern Woodlands. In the 17th century they lived in Pennsylvania, and in the 18th century they were in Pennsylvania, Ohio, Indiana and Illinois, with some bands in Kentucky a ...
s—made this agreement with the understanding that the British would leave the area after their war with the French.Instead of leaving the territory west of the
Appalachian Mountains The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...
as they had agreed, the Anglo-Americans remained on Native lands and reinforced their forts while settlers continued to push westward, despite the
Royal Proclamation of 1763 The Royal Proclamation of 1763 was issued by King George III on 7 October 1763. It followed the Treaty of Paris (1763), which formally ended the Seven Years' War and transferred French territory in North America to Great Britain. The Procla ...
placing a limit upon the westward expansion of the American colonies. The hostilities between the French and British declined significantly after 1760, followed by a final cessation of hostilities and the formal surrender of the French at the
Treaty of Paris Treaty of Paris may refer to one of many treaties signed in Paris, France: Treaties 1200s and 1300s * Treaty of Paris (1229), which ended the Albigensian Crusade * Treaty of Paris (1259), between Henry III of England and Louis IX of France * Trea ...
in February 1763. The attacks led by Pontiac against the British in early May 1763, near
Fort Detroit Fort Pontchartrain du Détroit or Fort Detroit (1701–1796) was a fort established on the north bank of the Detroit River by the French officer Antoine de la Mothe Cadillac and the Italian Alphonse de Tonty in 1701. In the 18th century, Fre ...
, mark what is generally considered to be the beginning of Pontiac's War. The siege of Fort Pitt and numerous other British forts during the spring and summer of 1763 were part of an effort by American Indians to reclaim their territory by driving the British out of the Ohio Country and back across the Appalachian Mountains. While many of the forts and outposts in the region were destroyed, the Indian effort to remove the British from Fort Pitt ultimately failed.


Diplomacy and siege

By May 27, the uprising reached the tribes near Fort Pitt, and there were many signs of impending hostilities. The captain of the Fort Pitt militia learned that the Delaware tribe just north of the fort had abandoned their dwellings and cornfields overnight. The Mingo had also abandoned their villages further up the river. The proprietor of the Pennsylvania provincial store reported that numerous Delaware warriors had arrived "in fear and haste" to exchange their skins for gunpowder and lead. The western Delaware warrior leaders Wolf and
Keekyuscung Keekyuscung (died 6 August, 1763) aka Kickyuscung, Kaquehuston, Kikyuskung, Ketiuscund, Kekeuscund, or Ketiushund, was a Delaware (Lenape) chief. In the 1750s he took part in peace negotiations to end Lenape participation in the French and Indian ...
had fewer than 100 warriors, so did not immediately attack the well-fortified Fort Pitt. Instead, on May 29, they attacked the supporting farms, plantations and villages in the vicinity of the fort. Panicked settlers crowded into the already overcrowded fort. Captain Simeon Ecuyer, a 22-year veteran Swiss mercenary in British service, tried to ready his fort after this news of expanding hostilities, putting his 230 men, half regulars and half quickly organized militia, on alert. The fort's exceptional structural defenses, made of stone with bastions covering all angles of attack, were supported by 16 cannons which he had permanently loaded. Ecuyer demolished the nearby village houses and structures to deny cover for attackers. He had trenches dug outside the fort, and set out beaver traps. Smallpox had been discovered within the fort, prompting Ecuyer to build a makeshift hospital in which to quarantine those infected. On the June 16, four Shawnee visited Fort Pitt and warned Alexander McKee and Captain Simeon Ecuyer that several Indian nations had accepted Pontiac's war belt and bloody hatchet and were going on the offensive against the British, but that the Delaware were still divided, with the older Delaware chiefs advising against war. The following day, however, the Shawnee returned and reported a more threatening situation, saying that all the nations "had taken up the hatchet" against the British, and were going to attack Fort Pitt. Even the local Shawnee themselves "were afraid to refuse" to join the uprising, a subtle hint that the occupants of Fort Pitt should leave. Ecuyer dismissed the warnings and ignored the requests to leave. On June 22, Fort Pitt was attacked on three sides by Shawnee, western Delaware, Mingo and Seneca, which prompted return fire from Ecuyer's artillery. This initial attack on the fort was repelled. Since the Indians were unfamiliar with siege warfare, they opted to try diplomacy yet again. On June 24,
Turtleheart Turtleheart (Turtle's Heart or Tortle's Heart, his unami name was ''Tahkoxitèh'') was a Delaware (Lenape) principal warrior and chief who lived during the French and Indian Wars, and Pontiac's War. He and Lenape Chief Killbuck represented the Del ...
spoke with McKee and Trent outside the fort, informing them that all of the other forts had fallen, and that Fort Pitt "is the only one you have left in our country." He warned McKee that "six different nations of Indians" were ready to attack if the garrison at the fort did not retreat immediately. They thanked Turtleheart and assured him that Fort Pitt could withstand "all nations of Indians", and they presented the Indian dignitaries with two small blankets and a handkerchief from the smallpox hospital. For the next several days it remained relatively quiet, although reports were coming in about fort after fort falling before large bands of attacking warriors. July 3, four Ottawa newcomers requested a
parley A parley (from french: link=no, parler – "to speak") refers to a discussion or conference, especially one designed to end an argument or hostilities between two groups of people. The term can be used in both past and present tense; in prese ...
and tried to trick the occupants of Fort Pitt into surrender, but the ruse failed. This was followed by several weeks of relative quiet, through July 18 when a large group of warriors arrived, likely from the Fort Ligonier area. McKee was informed by the Shawnee that the Indians were still hopeful of an amicable outcome, similar to agreements just made at Detroit. On July 26, a large conference headed by Ecuyer was convened with several leaders of the Ohioan tribes outside the walls of Fort Pitt. The Indian delegation,
Shingas Shingas ( fl. 17401763), was a Lenape chief and warrior who participated in military activities in Ohio Country during the French and Indian War. Allied with the French, Shingas led numerous raids on Anglo-American settlements during the war, for ...
, Wingenum and Grey Eyes among them, came to the fort under a flag of truce to parley, and again requested that the British leave this place. They explained that by taking the Indian's country the British caused this war, and Tessecumme of the Delaware noted that the British were the cause of the trouble since they had broken their promises and treaties. They had come onto Indian land and built forts, despite being asked not to, so now the tribes in the area have amassed to take back their lands. He informed Ecuyer that there was still a short time remaining to leave peacefully. The Delaware and Shawnee chiefs made sure Captain Ecuyer at Fort Pitt understood the cause of the conflict. Turtleheart told him, "You marched your armies into our country, and built forts here, though we told you, again and again, that we wished you to move, this land is ours, and not yours." The Delaware also let it be known, "that all the country was theirs; that they had been cheated out of it, and that they would carry on the war till they burnt Philadelphia". The British refused to leave, claiming that this was their home now. They bluffed that they could hold out for three years, and bragged that several large armies were coming to their aid. This "very much enraged" the Indian delegation, Trent wrote, "White Eyes and Wingenum seemed to be very much irritated and would not shake hands with our people at parting." On July 28, the siege began in earnest and continued for several days. Seven of the fort garrison were wounded, at least one mortally; Ecuyer was wounded in the leg by an arrow. For
Commander-in-Chief, North America The office of Commander-in-Chief, North America was a military position of the British Army. Established in 1755 in the early years of the Seven Years' War, holders of the post were generally responsible for land-based military personnel and ac ...
Jeffery Amherst Field Marshal Jeffery Amherst, 1st Baron Amherst, (29 January 1717 – 3 August 1797) was a British Army officer and Commander-in-Chief of the Forces in the British Army. Amherst is credited as the architect of Britain's successful campaign ...
, who before the war had dismissed the possibility that the Indians would offer any effective resistance to British rule, the military situation over the summer had become increasingly grim. The frustration was so great, he wrote to Colonel
Henry Bouquet Henry Bouquet (born Henri Louis Bouquet; 1719 – 2 September 1765) was a Swiss mercenary who rose to prominence in British service during the French and Indian War and Pontiac's War. He is best known for his victory over a Native American ...
and instructed him not to take any Indian prisoners. He proposed that they should be intentionally exposed to smallpox, hunted down with dogs, and "Every other method that can serve to Extirpate this Execrable Race." Amherst had directed Bouquet to take his troops to relieve Fort Pitt, a march that would take several weeks. At Fort Pitt, the siege didn't let up until August 1, 1763, when most of the Indians broke off their attack in order to intercept the body of almost 500 British troops marching to the fort under Colonel Bouquet. On August 5, these two forces met at Edge Hill in the
Battle of Bushy Run The Battle of Bushy Run was fought on August 5–6, 1763, in western Pennsylvania, between a British column under the command of Colonel Henry Bouquet and a combined force of Delaware, Shawnee, Mingo, and Huron warriors. This action occurred du ...
. Bouquet survived the attack and the Indians were unable to prevent his command from relieving Fort Pitt on August 10.


Aftermath

More than 500 British troops and perhaps a couple thousand settlers had died in the Ohio Valley, and of more than a dozen British forts, only Detroit, Niagara and Pitt remained standing at the height of this uprising. On October 7, 1763, the Crown issued
Royal Proclamation of 1763 The Royal Proclamation of 1763 was issued by King George III on 7 October 1763. It followed the Treaty of Paris (1763), which formally ended the Seven Years' War and transferred French territory in North America to Great Britain. The Procla ...
, which forbade all settlement west of the Appalachian Mountains—a proclamation ignored by British settlers, and unenforced by the British military. Fort Pitt would remain in British hands, and would become a central hub for migrant settlers as they pushed west in ever larger numbers over the next decade.


Biological warfare


Handoff of infirmary items

Sometime in the spring of 1763, a smallpox epidemic broke out near Fort Pitt and subsequently spread there. A smallpox hospital was then also established there to treat sick troops. There had also been an earlier epidemic among Ohio tribes in the early 1750s, as smallpox outbreaks occurred every dozen or so years. According to John McCullough, who was held captive, some of the Mahoning village warriors raiding a Juniata settlement caught smallpox from there that then killed some of them. In 1924 the ''
Mississippi Valley Historical Review ''The Journal of American History'' is the official academic journal of the Organization of American Historians. It covers the field of American history and was established in 1914 as the ''Mississippi Valley Historical Review'', the official jo ...
'' published a journal written by
William Trent William Trent (February 13, 1715–1787) was an American fur trader and merchant based in colonial Pennsylvania. He was commissioned as a captain of the Virginia Regiment in the early stages of the French and Indian War, when he served on the wes ...
, a fur trader and merchant commissioned as a captain at Fort Pitt. For June 24, 1763, Trent wrote about a meeting with two Delaware Indians at the fort. "Out of our regard to them we gave them two Blankets and an Handkerchief out of the Small Pox Hospital. I hope it will have the desired effect." (It was commonly believed in past centuries that smallpox could be readily spread at a distance through infected clothing or bedding. However, in the 1960s A. R. Rao’s detailed research, during the last years that smallpox was sufficiently prevalent for its mode of transmission to be studied, found no evidence for this mode of transmission. He concluded that it was a breath-borne disease, transmitted by "inhalation".) The two blankets and the handkerchief from the infirmary were seemingly wrapped in a piece of linen. The blankets and handkerchief were unwashed and dirty. In 1955 a record of Trent's trading firm was found. It had an invoice for the handkerchief, two blankets and the linen to be given to the Natives, and the expense was signed by Ecuyer. Ecuyer was relatively inexperienced, having only been a captain since April the year before and having taken over the command of the fort the same November. Trent was likely the main orchestrator of the idea, considering he had more experience with the disease and had even helped out setting the smallpox hospital. Half-Native Alexander McKee also played a part in parlaying messages, but he possibly didn't know about the items. This plan was carried out independently from General Amherst and Colonel Bouquet. The meeting happened on June 24. The night before "Two Delawares called for Mr. McKee and told him they wanted to speak to him in the Morning." The conference took place just outside of Fort Pitt. The participants were Ecuyer, McKee, Turtle's Heart, and another Delaware, "Mamaltee a Chief." The two Delaware men tried to coax the people holed up in the fort to leave, an option that Ecuyer promptly rejected and stated that reinforcements were coming to Fort Pitt and that the stronghold could easily hold out. After conferring with their chiefs, the two "returned and said they would hold fast of the Chain of friendship", but they were not genuinely believable. The messengers had asked for presents such as food and alcohol, "to carry us Home." Requesting gifts was common, but Ecuyer in this case seemed especially generous. Turtle's Heart and his companion received food in "large quantities", some "600 Rations." Included among this was the linen bundle containing the handkerchief and two blankets. A month after meeting on July 22, Trent met with the same delegates again and they seemingly had not contracted smallpox: "Gray Eyes, Wingenum, Turtle's Heart and Mamaultee, came over the River told us their Chiefs were in Council, that they waited for Custaluga who they expected that Day." Gershom Hicks, who was fluent in the Delaware language and also knew some Shawnee, testified that starting from spring 1763 up to April 1764 around a hundred Natives from different tribes such as
Lenni Lenape The Lenape (, , or Lenape , del, Lënapeyok) also called the Leni Lenape, Lenni Lenape and Delaware people, are an indigenous peoples of the Northeastern Woodlands, who live in the United States and Canada. Their historical territory inclu ...
(Delaware) and
Shawnee The Shawnee are an Algonquian-speaking indigenous people of the Northeastern Woodlands. In the 17th century they lived in Pennsylvania, and in the 18th century they were in Pennsylvania, Ohio, Indiana and Illinois, with some bands in Kentucky a ...
died in the smallpox epidemic, making it a relatively minor smallpox outbreak. After visiting Pittsburgh a few years later, David McClure would write in his journal published in 1899, "I was informed at Pittsburgh, that when the Delawares, Shawanese & others, laid siege suddenly and most traitorously to Fort Pitt, in 1764, in a time of peace, the people within, found means of conveying the small pox to them, which was far more destructive than the guns from the walls, or all the artillery of Colonel Boquet's army, which obliged them to abandon the enterprise."


Amherst letters

A month later in July Colonet Bouquet discussed Pontiac's War in detail with General Amherst via letters, and in postscripts of three letters in more freeform style Amherst also briefly broached the subject of using of smallpox as a weapon. Bouquet brought up blankets as a means without going into specifics, and Amherst supported the idea "to Extirpate this Execreble Race". Bouquet himself probably never had the opportunity to "Send the Small Pox." He was very concerned about smallpox, having never had it. When Bouquet wrote to Ecuyer, he didn't mention the disease. He died only two years later in 1765 of
yellow fever Yellow fever is a viral disease of typically short duration. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains – particularly in the back – and headaches. Symptoms typically improve within five days. In ...
.


Later assessments

This event is usually described as an early attempt at biological warfare. However the plan's effectiveness is generally questioned.


Early research

The account of the British infecting Natives with smallpox during Pontiac's War of 1763 originated with nineteenth century historian
Francis Parkman Francis Parkman Jr. (September 16, 1823 – November 8, 1893) was an American historian, best known as author of '' The Oregon Trail: Sketches of Prairie and Rocky-Mountain Life'' and his monumental seven-volume '' France and England in North Am ...
. His account has been relied on by later writers. He described Amherst's reply to Bouquet as a “detestable suggestion” and concluded "There is no direct evidence that Bouquet carried into effect the shameful plan of infecting the Indians though, a few months after, the small-pox was known to have made havoc among the tribes of the Ohio." Parkman had the impression that Amherst had planned the gifting, although Amherst approached the matter only a month later. Following Parkman was Howard Peckham who was more interested in the overall war and paid only cursory glance to the incident, briefly describing Ecuyer handing over the handkerchief and blankets from the smallpox hospital. He quoted a testimony of a smallpox outbreak and stated that it certainly affected the Natives' ability to wage war. Bernhard Knollenberg was more critical and pointed out that both Parkman and Peckham hadn't noticed that the smallpox epidemic among the tribes had been reported to have begun in the spring of 1763, quite some time before the meeting. Knollenberg even doubted the authenticity of the documents at first before he was contacted via letter by historian Donald H. Kent who had found a record of Trent's sundries list signed by Ecuyer.


Later researchers

Francis Jennings Francis "Fritz" Jennings (1918November 17, 2000) was an American historian, best known for his works on the colonial history of the United States. He taught at Cedar Crest College from 1968 to 1976, and at the Moore College of Art from 1966 to 1 ...
, a historian who extensively studied Parkman's writings, had a more damning view. He indicated that the fighting strength of the Natives was greatly compromised by the plan. Microbiologist
Mark Wheelis Mark L. Wheelis is an American microbiologist. Wheelis is currently a professor in the College of Biological Sciences, University of California, Davis. Carl Woese and Otto Kandler with Wheelis wrote the important paper '' Towards a natural system of ...
says the act of biological aggression at Fort Pitt is indisputable, but that at the time the rare attempts to transmit infection rarely worked and they were probably made redundant with natural routes of transmission. The practice was restrained by lack of knowledge.
Elizabeth A. Fenn Elizabeth Anne Fenn (born September 22, 1959) is an American historian. Her book '' Encounters at the Heart of the World: A History of the Mandan People'', won the 2015 Pulitzer Prize for History. She serves as the Walter S. and Lucienne Driskill ...
writes that "the actual effectiveness of an attempt to spread smallpox remains impossible to ascertain: the possibility always exists that infection occurred by some natural route." Philip Ranlet describes as a clear sign that the blankets had no effect the fact that the same delegates were met a month later, and that nearly all of the met natives were recorded to have lived for decades afterwards. He also questions why Trent didn't gloat about any possible success in his journal if there was such. David Dixon holds likely that the transmission happened via some other route and possibly from the event described by John McCullough. Barbara Mann holds that the distribution worked, describing that Gershom Hick's testimony of the epidemic starting by spring is explainable by Hicks lacking a calendar. Mann also estimates that papers related to the incident have been destroyed. Researchers James W. Martin, George W. Christopher and Edward M. Eitzen writing in a publication for the US Army Medical Department Center & School,
Borden Institute The Borden Institute is a U.S. Army “Center of Excellence in Military Medical Research and Education”. In 1987, U.S. Army Colonel Russ Zajtchuk conceived the idea for a “Center of Excellence in Military Medical Research and Education,” u ...
, found that "In retrospect, it is difficult to evaluate the tactical success of Captain Ecuyer's biological attack because smallpox may have been transmitted after other contacts with colonists, as had previously happened in New England and the South. Although scabs from smallpox patients are thought to be of low infectivity as a result of binding of the virus in fibrin metric, and transmission by fomites has been considered inefficient compared with respiratory droplet transmission." In an article published in the journal '' Clinical Microbiology and Infection'' researchers Vincent Barras and Gilbert Greub conclude that “in the light of contemporary knowledge, it remains doubtful whether his hopes were fulfilled, given the fact that the transmission of smallpox through this kind of vector is much less efficient than respiratory transmission, and that Native Americans had been in contact with smallpox >200 years before Ecuyer’s trickery, notably during
Pizarro Francisco Pizarro González, Marquess of the Atabillos (; ;  – 26 June 1541) was a Spanish conquistador, best known for his expeditions that led to the Spanish conquest of Peru. Born in Trujillo, Spain to a poor family, Pizarro chose ...
’s conquest of South America in the 16th century. As a whole, the analysis of the various ‘pre-microbiological” attempts at BW illustrate the difficulty of differentiating attempted biological attack from naturally occurring epidemics.”


Citations


References

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External links

* NativeWeb documents on
Amherst-Bouquet

Fort Pitt



Bouquet Papers

Global Biosecurity: Threats and Responses
Katona, Peter; Routledge * Ecuyer, Simeon: Fort Pitt and letters from the frontier (1892)
Entry June 2, 1763

Entry of June 24, 1763

"Colonial Germ Warfare"
article from Colonial Williamsburg Journal


History of that part of the Susquehanna and Juniata valleys, embraced in the counties of Mifflin, Juniata, Perry, Union and Snyder, in the commonwealth of Pennsylvania
Everts, Peck & Richards; 1886
Pioneers of Second Fork
James P. Burke

{{Pennsylvania during the French and Indian War Fort Pitt Biological warfare History of Pittsburgh Fort Pitt 1763 Fort Pitt Smallpox Fort Pitt 1763 in North America British war crimes Native American genocide