My basis was this account, which I heard while attending elementary school in Colorado in 1957...
Colonial weaponizing of smallpox against Native Americans was first reported by 19th-century historian Francis Parkman. Parkman came across correspondence in which Sir Jeffery Amherst, commander in chief of the British forces in North America in the early 1760s, discussed its use with Col. Henry Bouquet, a subordinate on the western frontier during the French and Indian War.In the late spring of 1763, Delaware, Shawnee and Mingo warriors, inspired by Ottawa war leader Pontiac, laid siege to Fort Pitt, an outpost at the confluence of the Allegheny and Monongahela rivers in present-day downtown Pittsburgh. The fort’s commander, Capt. Simeon Ecuyer, reported in a June 16 message to his superior, Philadelphia-based Col. Henry Bouquet, that the situation was dire, with local traders and colonists taking refuge inside the fort’s walls. Ecuyer wasn’t just afraid of his Native American adversaries. The fort’s hospital had patients with smallpox, and Ecuyer feared the disease might overwhelm the population inside the fort’s cramped confines.
Bouquet, in turn, passed along the news about smallpox inside Fort Pitt to his own superior, Amherst, in a June 23 letter. In Amherst’s July 7 response, he cold-bloodedly saw an opportunity in the disease outbreak. “Could it not be contrived to Send the Small Pox among those Disaffected Tribes of Indians? We must, on this occasion, Use Every Stratagem in our power to Reduce them.”
On July 13, Bouquet, who at that point was traveling across Pennsylvania with British reinforcements for Fort Pitt, responded to Amherst, promising that he would try to spread the disease to the Native Americans via contaminated blankets, “taking care however not to get the disease myself.” That tactic seemed to please Amherst, who wrote back in approval on July 16, urging him to spread smallpox “as well as try Every other method that can serve to Extirpate this Execreble [sic] Race.”
What Amherst and Bouquet didn’t know was that somebody at Fort Pitt had already thought of trying to infect the Native Americans with smallpox—and had attempted to do it.
You should do more research, even your one account doesn’t hold up, and it doesn’t support your initial claim, did you get that from history.com?
Medved examines the evidence and concludes “The endlessly recycled charges of biological warfare rest solely on controversial interpretations of two unconnected and inconclusive incidents 74 years apart.”
The first was in response to Pontiac’s Rebellion (1763), a ferocious small war undertaken by the Great Lakes Indians (who had been allied with the defeated French in the French and Indian War) against British settlements. The Ottawa leader Pontiac told his followers to “exterminate” the whites. They did their best. Hundreds of settlers were tortured, scalped, cannibalized, dismembered, or burned at the stake. As the Indians were besieging Fort Pitt, Field Marshal Lord Jeffery Amherst wrote to a subordinate, “Could it not be contrived to send the Small Pox among the disaffected tribes of Indians?” But nothing seems to have come from this correspondence.