Fort Detroit the Native Americans to trap and hunt, as well as rendering them less of a threat. The British colonists did not emphasize maintaining good relationships with the Native Americans. But the French Canadians had formed many families through intermarriage and knew about the Native American custom of giving gifts. After the French left the conflict, Pontiac war-leader of the Ottawa, rallied several tribes in Pontiac's Rebellion. He attempted to capture Detroit from the British on May 7, 1763. They failed to capture the fort, as the British were forewarned of the attack, but did lay siege to it (see 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