The British military routinely inoculated its own troops against smallpox, exposing soldiers to the pus from smallpox pustules to induce mild cases of the disease and, once the soldiers recovered, lifelong immunity. In Boston, and perhaps also Quebec, the British also appear to have forced smallpox on civilians, hoping to spread disease to rebel troops.
In Boston the mission seems to have failed; infected civilians were quarantined and kept from Continental soldiers. But in Quebec, smallpox swept through the Continental Army, helping to prompt a retreat.
Earlier in the century, the British similarly targeted Native Americans. In an infamous case of 1763, at Fort Pitt on the Pennsylvania frontier, Gen. Jeffery Amherst (pictured above) ordered that blankets and handkerchiefs from smallpox patients in the fort's infirmary be given to Delaware Indians at a peace-making parley.