Siege of Fort Detroit command of Captain James Dalyell arrived at Fort Detroit. On July 31, 1763, about 250 men attempted to make a surprise attack on Pontiac's encampment. Pontiac was ready and waiting with over 400 warriors, and defeated the British at the Battle of Bloody Run. However, the situation at the fort remained a stalemate, and Pontiac's influence among his followers began to wane. Groups of Indians began to abandon the siege, some of them making peace with the British before departing. On October 31, 1763, finally convinced that the French in Illinois would not come to his aid, Pontiac lifted the
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