Final answer:
The largest Canadian military deployment on Canadian soil was related to the conscription crisis during World War I, involving widespread controversy over mandatory enlistment and an increased medical services presence due to the Halifax Explosion and other war-related injuries.
Step-by-step explanation:
The largest Canadian military deployment on Canadian soil, that wasn't in response to a natural disaster, was likely during World War I related to the conscription crisis of 1917.
With the mounting casualties on the Western Front and the volunteer enlistments not keeping up with the demand for troops, the Canadian government under Prime Minister Sir Robert Borden introduced conscription to ensure more soldiers could be sent to Europe.
This led to widespread controversy, particularly in Quebec, where the majority were farmers or did not share the same enthusiasm for the war effort as other parts of Canada.
Adding to the military activity within Canada, women also prepared to defend the nation against potential German invasion, forming paramilitary organizations and learning to handle firearms. A notable figure, Jessie McNab, organized groups of women in Toronto for this purpose.
Furthermore, medical services within Canada were scaled up as by the end of World War I, there were sixty-five military hospitals employing 527 nurses to treat the influx of patients, including those affected by the Halifax Explosion in December 1917.
Conscription and preparation for defense against invasion constituted significant military activities within Canada during this period, illustrating the country’s response to the global conflict and the impact it had on Canadian society and politics.