From the earliest years of colonialism, conquistadores like Vasco Núñez de Balboa would brazenly advocate genocide against the native population.[50] In the 1700s, British militia like William Trent and Simeon Ecuyer gave Smallpox-exposed blankets to Native American emissaries as gifts at Fort Pitt, "to Convey the Smallpox to the Indians", in one of the most famously documented cases of germ warfare. While it is uncertain how successful such attempts were against the target population,[51] historians have noted that, "history records numerous instances of the French, the Spanish, the English, and later on the American, using smallpox as an ignoble means to an end. For smallpox was more feared by the Indian than the bullet: he could be exterminated and subjugated more easily and quickly by the death-bringing virus than by the weapons of the white man."[52] The British High Commander Jeffery Amherst authorized the intentional use of disease as a biological weapon against indigenous populations during the Pontiac's Rebellion, saying, "You will Do well to try to Innoculate the Indians by means of Blanketts, as well as to try Every other method that can serve to Extirpate this Execreble Race", and instructing his subordinates, "I need only Add, I Wish to Hear of no prisoners should any of the villains be met with arms."[53][54] When smallpox swept the northern plains of the US in 1837, Secretary of War Lewis Cass ordered that the Mandan (along with the Arikara, the Cree, and the Blackfeet) not be given smallpox vaccinations, which had been provided to other tribes in other areas.[55][56][57]