Fort Pitt (Pennsylvania) among Native Americans devastated the tribes of Ohio Valley and the Great Lakes areas. On August 1, 1763, most of the American Indians broke off the siege to intercept the approaching force under Colonel Bouquet. In the Battle of Bushy Run, Bouquet fought off the American Indian attack and relieved Fort Pitt on August 10. In 1772, after Pontiac's War, the British commander at Fort Pitt sold the building to two colonists, William Thompson and Alexander Ross. At that time, the Pittsburgh area was claimed by the colonies of both Virginia and Pennsylvania, which struggled for power over the region.
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