Today Canada and The United States are the best of friends, but it wasn't always this way.
At one point the two countries had a plan to attack one another if the need arose.
War Plan Red was one of a number of U.S. color-coded war plans developed by the U.S. after the First World War.
When War Plan Red was declassified in 1974, it caused a stir in American–Canadian relations because Canada, codenamed "Crimson" in the plan, was to have been the principal target of American forces.
War Plan Red first set out a description of Canada's geography, military resources, and transportation, and went on to evaluate a series of possible pre-emptive American campaigns to invade Canada in several areas and occupy key ports and railways before British troops could provide reinforcement to the Canadians
A key move was a joint U.S. army-navy attack to capture the port city of Halifax, cutting off the Canadians from their British allies. Their next objective was to "seize Canadian Power Plants near Niagara Falls" This was to be followed by a full-scale invasion on three fronts: From Vermont to take Montreal and Quebec, from North Dakota to take over the railhead at Winnipeg, and from the Midwest to capture the strategic nickel mines of Ontario. In parallel, the U.S. Navy was to seize the Great Lakes and blockade Canada’s Atlantic and Pacific ports.
Canadian military officer Lieutenant Colonel James "Buster" Sutherland Brown developed an earlier counterpart to War Plan Red called Defence Scheme No. 1 on April 12, 1921. Maintaining that the best defense was a good offense, "Buster" Brown planned for rapid deployment of flying columns to occupy Seattle, Great Falls, Minneapolis, and Albany. With no hope of holding these objectives, the idea was to divert American troops to the flanks and away from Canada, hopefully long enough for Imperial allies to arrive with reinforcements. Defence Scheme No. 1 was terminated by Chief of the General Staff Andrew McNaughton in 1928, two years prior to the approval of War Plan Red.