The eighteenth century historical documents fail to support the view, advanced by David Mandelbaum and others, that the Cree and Assiniboin invaded the west after 1690 as a result of the introduction of the fur trade. This view, widely supported by nineteenth century authorities, can be traced to several brief ambiguous statements published in 1801 by Alexander Mackenzie. The western limits of the Cree and Assiniboin in the early 1700s remain unclear. Their marauding activities against members of the Blackfoot Confederacy began in the late 1700s, almost fifty years after they were documented as peacefully living in central Alberta. Although their northern limits are unknown, the Cree seem always to have strained relations with neighbouring Athabaskans. In the mid?770s, six major Cree groups inhabited the western parklands, plains and boreal forest: the Susuhana, Sturgeon, Pegogamaw, Keskachewan/Beaver, Athabaska and Missinipi. These groups were all obliterated by the smallpox epidemic of 1781, and it was the resultant population shifts, which were noted by nineteenth century observers.