In 1956 analysts with the Defence Research Board (DRB), the scientific and technical branch of the Canadian armed services, recommended the creation of a national grid system for the recording and reporting of atmospheric fallout resulting from an atomic weapons detonation over or near Canada.

Fearing a full-scale nuclear attack on Canada and contiguous areas of the United States, senior officials in the Department of National Defence (DND) accepted the recommendations and implemented a plan to devise a Canadian policy for reporting nation-wide fallout levels during an emergency.

The documents provided in this briefing book trace a decade-long effort in Ottawa to craft Canada's official policy for fallout reporting and subsequent emergency measures response during the Cold War. The records begin in 1959 and run through 1969, offering insight into the military decisions and priorities that shaped a significant period in Canadian security and world affairs.