Fort Pitt Museum Pitt, after William Pitt the Elder. As a result, in 1763 local Delawares and Shawnees took part in Pontiac's Rebellion, an effort to drive the British out of their territory. The Indians' siege of Fort Pitt began on June 22, 1763, but the fort was too strong to be taken by force. In negotiations during the siege, the commander of Fort Pitt gave two Delaware emissaries blankets that had been exposed to smallpox, in hopes of infecting the surrounding Indians and ending the siege. The effectiveness of this attempt is unclear. Outbreaks of smallpox had plagued Native Americans for years
Siege of Fort Pitt become by 1763 and how far British officers were willing to go in ignoring their own soldiers' code of warfare. A devastating smallpox epidemic plagued Native American tribes in the Ohio Valley and Great Lakes area through 1763 and 1764, but the effectiveness of these instances of efforts to spread smallpox remain unknown. After extensive review of surviving documentary evidence, historian Francis Jennings concluded the attempt at biological warfare was "unquestionably effective at Fort Pitt"; Barbara Mann deduced "it is important to note that the smallpox distribution worked"; Howard Peckham noted the resulting fatal epidemic "certainly affected their vigorous prosecution