The decades following the Rebellions of 1837–1838 marked the start of intelligence services in Canada. Defeat in the failed uprising caused the restoration of colonial regimes and the reform of imperialism. As a result, informal intelligence services were formed to conduct certain activities. 1864 marked the formation of two secret police forces and the formal intelligence service in Canada. Created to protect the Canada–United States border, these organization were under the control of a Montreal police commander and political ally. In response to a number of raid and attacks connected with Irish nationalism, Prime Minister John A. Macdonald merged the two forces to form the Dominion Police (DP). The DP was subsequently merged with the North-West Mounted Police to form the Royal North-West Mounted Police in 1904 and the Royal Canadian Mounted Police (RCMP) in 1920.
During the World War II period, ties with allied intelligence strengthened. Canadian intelligence services, usually following in the way that the British collect information, began to follow the ways of the United States' system; new governmental committees were established and Canadians served in a variety of intelligence capacities, both home and abroad. Camp X, a secret training facility in Ontario, in an example of such joint activities. The camp led to the establishment of the Communications Security Establishment, scientific cooperation in the Manhattan Project and the establishment of the first biological germ warfare station. The 1945 defection of Soviet cipher clerk, Igor Gouzenko served as the catalyst of major structural reform to the security and intelligence system and led to the formation of one of several royal commissions to investigate the activities of foreign intelligence networks in Canada. Recognition came to the RCMP's Intelligence Section when it was elevated to branch status and then re-established as the Directorate of Security and Intelligence or the "I" Directorate. Following a 1969 report, the DSI became the RCMP Security Service and was further elevated from regional-level division to national-level division giving the director even more power.
In 1984, the RCMP Security Service was disbanded to make way for the Canadian Security Intelligence Service. This reform was caused by a report released by the McDonald Commission in 1981. The Department of National Defence and the Canadian Forces have two main agencies responsible for providing intelligence: the Communications Security Establishment, which is responsible for the signals intelligence aspects of military intelligence and the Canadian Forces Intelligence Command which is the main intelligence service of the Canadian Forces. The Int Branch, as it is sometimes referred as, conduct operations both home and abroad to provide correct and up-to-date information to defence operation planners and commanders.