Up until 1870, the region was nominally under the control of the Hudson's Bay Company, although there was essentially no law enforcement. In 1873 a skirmish between white and Métis traders and members of the Assiniboine First Nation, which came to be known as the Cypress Hills Massacre, prompted Prime Minister John A. Macdonald to create the North-West Mounted Police. In 1875 they established Fort Walsh, named after its builder, Inspector James Morrow Walsh. The following year, when Sioux leader Sitting Bull led his people into Canada after the Battle of Little Big Horn, they arrived at Fort Walsh. Sitting Bull and James Walsh became such good friends that Walsh was criticized for not pursuing Canadian government policy and forcing the Sioux back into the United States.